## THE DISTRIBUTIVE LAW

If we want to multiply a amount by another number, either we can multiply each term the the amount by the number before we include or we can first add the terms and also then multiply. Because that example, In either situation the result is the same.

You are watching: Factor x^2+x-6

This property, i m sorry we an initial introduced in section 1.8, is referred to as the distributive law. In symbols,

a(b + c) = abdominal muscle + ac or (b + c)a = ba + ca

By applying the distributive legislation to algebraic expression containing parentheses, we can achieve equivalent expressions there is no parentheses.

Our very first example requires the product of a monomial and also binomial.

Example 1 write 2x(x - 3) there is no parentheses.

Solution

We think of 2x(x - 3) as 2x and also then apply the distributive legislation to obtain The above technique works equally too with the product that a monomial and trinomial.

Example 2 compose - y(y2 + 3y - 4) without parentheses.

Solution

Applying the distributive property yields When simplifying expressions including parentheses, we an initial remove the parentheses and also then combine like terms.

Example 3 simplify a(3 - a) - 2(a + a2).

We begin by remove parentheses come obtain Now, combining like terms yields a - 3a2.

We deserve to use the distributive residential or commercial property to rewrite expression in i beg your pardon the coefficient of one expression in parentheses is +1 or - 1.

Example 4 compose each expression without parentheses.a. +(3a - 2b)b. -(2a - 3b)

Solution Notice the in example 4b, the authorize of every term is adjusted when the expression is created without parentheses. This is the same an outcome that we would have acquired if we offered the measures that we introduced in ar 2.5 to leveling expressions.

## FACTORING MONOMIALS from POLYNOMIALS

From the symmetric building of equality, we recognize that if

a(b + c) = abdominal + ac, then abdominal muscle + ac = a(b + c)

Thus, if over there is a monomial factor typical to all terms in a polynomial, we have the right to write the polynomial together the product that the usual factor and also another polynomial. Because that instance, because each term in x2 + 3x consists of x as a factor, we can write the expression together the product x(x + 3). Rewriting a polynomial in this method is called factoring, and the number x is claimed to be factored "from" or "out of" the polynomial x2 + 3x.

To aspect a monomial from a polynomial:Write a collection of parentheses preceded by the monomial usual to each term in the polynomial.Divide the monomial element into each term in the polynomial and also write the quotient in the parentheses.Generally, we can find the common monomial aspect by inspection.

Example 1 a. 4x + 4y = 4(x + y) b. 3xy -6y - 3y(x - 2)

We can examine that us factored effectively by multiply the factors and verifyingthat the product is the original polynomial. Using instance 1, we get If the typical monomial is difficult to find, we deserve to write every term in element factored kind and note the common factors.

Example 2 aspect 4x3 - 6x2 + 2x.

equipment We deserve to write We currently see the 2x is a usual monomial factor to all 3 terms. Climate we variable 2x the end of the polynomial, and write 2x()

Now, we divide each hatchet in the polynomial through 2x and compose the quotients inside the parentheses come get

2x(2x2 - 3x + 1)

We can check our answer in example 2 by multiply the components to obtain In this book, we will certainly restrict the common factors come monomials consisting of number coefficients that space integers and to integral powers of the variables. The selection of authorize for the monomial variable is a issue of convenience. Thus,

-3x2 - 6x

can be factored either as

-3x(x + 2) or as 3x(-x - 2)

The an initial form is usually more convenient.

Example 3Factor out the common monomial, including -1.

a. - 3x2 - 3 xyb. -x3 - x2 + x equipment Sometimes the is practically to compose formulas in factored form.

Example 4 a. A = p + PRT = P(1 + RT) b. S = 4kR2 - 4kr2 = 4k(R2 - r2)

## 4.3BINOMIAL products I

We have the right to use the distributive regulation to multiply two binomials. Although over there is little need to multiply binomials in arithmetic as presented in the example below, the distributive law additionally applies to expression containing variables. We will certainly now apply the over procedure for an expression comprise variables.

Example 1

Write (x - 2)(x + 3) there is no parentheses.

Solution First, apply the distributive residential or commercial property to obtain Now, integrate like terms to obtain x2 + x - 6

With practice, you will have the ability to mentally include the second and 3rd products. Theabove process is sometimes called the silver paper method. F, O, I, and L stand for: 1.The product that the first terms.2.The product that the external terms.3.The product the the within terms.4.The product the the critical terms.

The FOIL method can likewise be supplied to square binomials.

Example 2

Write (x + 3)2 without parentheses.Solution

First, rewrite (x + 3)2 together (x + 3)(x + 3). Next, apply the FOIL an approach to get Combining choose terms yieldsx2 + 6x + 9

When we have a monomial factor and two binomial factors, the is easiest to first multiply the binomials.

Example 3

write 3x(x - 2)(x + 3) without parentheses.Solution First, main point the binomials come obtain3x(x2 + 3x - 2x - 6) = 3x(x2 + x - 6)

Now, apply the distributive legislation to get 3x(x2 + x - 6) = 3x3 + 3x2 - 18x

Common Errors

Notice in example 2 Similarly, In general, ## 4.4FACTORING TRINOMIALS ns

In section 4.3, us saw just how to uncover the product of two binomials. Now we will certainly reverse this process. That is, given the product of two binomials, we will discover the binomial factors. The process involved is an additional example that factoring. As before,we will only consider factors in which the terms have actually integral numerical coefficients. Such factors do not always exist, but we will examine the cases where lock do. Notice that the first term in the trinomial, x2, is product (1); the critical term in thetrinomial, 12, is product and the center term in the trinomial, 7x, is the amount of assets (2) and also (3).In general, We usage this equation (from appropriate to left) to factor any kind of trinomial that the type x2 + Bx + C. We uncover two numbers who product is C and also whose amount is B.

Example 1 factor x2 + 7x + 12.Solution us look for 2 integers whose product is 12 and also whose amount is 7. Take into consideration the following pairs of components whose product is 12. We view that the just pair of determinants whose product is 12 and also whose amount is 7 is 3 and also 4. Thus,

x2 + 7x + 12 = (x + 3)(x + 4)

Note that when all terms of a trinomial space positive, we require only take into consideration pairs of confident factors due to the fact that we are looking for a pair of factors whose product and sum space positive. The is, the factored hatchet of

x2 + 7x + 12would be of the form

( + )( + )

When the very first and third terms the a trinomial room positive yet the middle term is negative, we need only think about pairs of an unfavorable factors since we are looking for a pair of factors whose product is positive yet whose amount is negative. That is,the factored type of

x2 - 5x + 6

would be of the form

(-)(-)

Example 2 element x2 - 5x + 6.

Solution due to the fact that the third term is positive and also the middle term is negative, we find two negative integers who product is 6 and also whose amount is -5. Us list the possibilities. We check out that the only pair of components whose product is 6 and whose sum is -5 is -3 and also -2. Thus,

x2 - 5x + 6 = (x - 3)(x - 2)

When the very first term the a trinomial is positive and also the 3rd term is negative,the indications in the factored form are opposite. That is, the factored kind of

x2 - x - 12

would be of the form

(+)(-) or (-)(+)

Example 3

Factor x2 - x - 12.

Solution us must discover two integers who product is -12 and whose sum is -1. We list the possibilities. We see that the only pair of determinants whose product is -12 and also whose sum is -1 is -4 and 3. Thus,

x2 - x - 12 = (x - 4)(x + 3)

It is easier to factor a trinomial totally if any monimial factor common to every term the the trinomial is factored first. Because that example, us can aspect

12x2 + 36x + 24

as A monomial deserve to then be factored from these binomial factors. However, very first factoring the usual factor 12 from the initial expression returns

12(x2 + 3x + 2)

Factoring again, we have

12(* + 2)(x + 1)

which is said to be in fully factored form. In such cases, that is not necessary to element the numerical element itself, that is, we perform not write 12 together 2 * 2 * 3.

instance 4

element 3x2 + 12x + 12 completely.

SolutionFirst we factor out the 3 indigenous the trinomial to get

3(x2 + 4x + 4)

Now, we variable the trinomial and also obtain

3(x + 2)(x + 2)

The approaches we have developed are also valid because that a trinomial such as x2 + 5xy + 6y2.

Example 5Factor x2 + 5xy + 6y2.

Solution We uncover two positive determinants whose product is 6y2 and whose sum is 5y (the coefficient that x). The two determinants are 3y and 2y. Thus,

x2 + 5xy + 6y2 = (x + 3y)(x + 2y)

once factoring, that is ideal to create the trinomial in descending strength of x. If the coefficient that the x2-term is negative, factor out a an unfavorable before proceeding.

Example 6

Factor 8 + 2x - x2.

Solution We first rewrite the trinomial in descending strength of x come get

-x2 + 2x + 8

Now, we can variable out the -1 come obtain

-(x2 - 2x - 8)

Finally, we element the trinomial to yield

-(x- 4)(x + 2)

Sometimes, trinomials space not factorable.

Example 7

Factor x2 + 5x + 12.

Solution we look for two integers whose product is 12 and whose amount is 5. Indigenous the table in example 1 on page 149, we watch that there is no pair of components whose product is 12 and also whose sum is 5. In this case, the trinomial is not factorable.

Skill at factoring is typically the an outcome of considerable practice. If possible, do the factoring procedure mentally, creating your prize directly. Girlfriend can check the results of a factorization by multiplying the binomial factors and verifying the the product is equal to the provided trinomial.

## 4.5BINOMIAL products II

In this section, we use the procedure developed in section 4.3 to main point binomial factors whose first-degree terms have numerical coefficients various other than 1 or - 1.

Example 1

Write as a polynomial.

a. (2x - 3)(x + 1)b. (3x - 2y)(3x + y)

Solution

We an initial apply the FOIL an approach and then combine like terms. As before, if we have actually a squared binomial, we an initial rewrite it as a product, then use the foil method.

Example 2

a. (3x + 2)2 = (3x + 2)(3x + 2) = 9x2 + 6x + 6x + 4 = 9x2 + 12x + 4

b. (2x - y)2 = (2x - y)(2x - y) = 4x2 - 2xy - 2xy + y2 - 4x2 - 4xy + y2

As girlfriend may have actually seen in ar 4.3, the product of two bionimals may have no first-degree term in the answer.

Example 3

a. (2x - 3)(2x + 3) = 4x2 + 6x - 6x - 9 = 4x2 -9

b. (3x - y)(3x + y) - 9x2 + 3xy - 3xy - y2= 9x2 - y2

When a monomial factor and two binomial determinants are gift multiplied, it iseasiest to multiply the binomials first.

Example 4

Write 3x(2x - l)(x + 2) together a polynomial.

Solution We very first multiply the binomials come get3x(2x2 + 4x - x - 2) = 3x(2x2 + 3x - 2)Now multiplying by the monomial yields3x(2x2) + 3x(3x) + 3x(-2) = 6x3 + 9x2 - 6x

## 4.6FACTORING TRINOMIALS II

In section 4.4 we factored trinomials of the form x2 + Bx + C wherein the second-degree term had a coefficient that 1. Currently we want to prolong our factoring techniquesto trinomials that the form Ax2 + Bx + C, whereby the second-degree term has acoefficient various other than 1 or -1.

First, we take into consideration a test to identify if a trinomial is factorable. A trinomial ofthe type Ax2 + Bx + C is factorable if us can discover two integers who product isA * C and whose sum is B.

Example 1

Determine if 4x2 + 8x + 3 is factorable.

Solution We examine to watch if there room two integers who product is (4)(3) = 12 and whosesum is 8 (the coefficient of x). Think about the complying with possibilities. Since the components 6 and 2 have actually a sum of 8, the value of B in the trinomialAx2 + Bx + C, the trinomial is factorable.

Example 2

The trinomial 4x2 - 5x + 3 is not factorable, since the over table reflects thatthere is no pair of determinants whose product is 12 and also whose sum is -5. The check tosee if the trinomial is factorable can usually be excellent mentally.

Once we have established that a trinomial of the type Ax2 + Bx + C is fac-torable, we continue to uncover a pair of components whose product is A, a pair the factorswhose product is C, and also an arrangement that yields the appropriate middle term. Weillustrate by examples.

Example 3

Factor 4x2 + 8x + 3.

Solution Above, we established that this polynomial is factorable. We currently proceed. 1. We think about all pairs of determinants whose product is 4. Due to the fact that 4 is positive, just positive integers have to be considered. The possibilities space 4, 1 and 2, 2.2. We consider all pairs of factors whose product is 3. Due to the fact that the center term is positive, consider positive bag of components only. The possibilities space 3, 1. We write all possible arrangements of the factors as shown. 3. We pick the setup in i beg your pardon the amount of assets (2) and (3) yields a middle term that 8x.

Now, we consider the administrate of a trinomial in which the constant term is negative.

Example 4

Factor 6x2 + x - 2.

Solution First, us test to check out if 6x2 + x - 2 is factorable. We look for two integers the havea product the 6(-2) = -12 and a sum of 1 (the coefficient that x). The integers 4 and-3 have a product that -12 and a amount of 1, therefore the trinomial is factorable. Us nowproceed. We take into consideration all bag of determinants whose product is 6. Since 6 is positive, just positive integers should be considered. Then possibilities are 6, 1 and also 2, 3.We take into consideration all pairs of components whose product is -2. The possibilities room 2, -1 and also -2, 1. We write all feasible arrange ments the the determinants as shown.We select the arrangement in i beg your pardon the amount of products (2) and (3) returns a middle term that x.

With practice, friend will have the ability to mentally examine the combinations and also will notneed to write out every the possibilities. Paying fist to the signs in the trinomialis an especially helpful because that mentally eliminating feasible combinations.

It is simplest to variable a trinomial composed in descending powers of the variable.

Example 5

Factor.

a. 3 + 4x2 + 8x b. X - 2 + 6x2

Solution Rewrite every trinomial in descending strength of x and also then monitor the remedies ofExamples 3 and also 4.

a. 4x2 + 8x + 3 b. 6x2 + x - 2

As we said in section 4.4, if a polynomial has a typical monomial factorin each of that is terms, us should element this monomial from the polynomial beforelooking for other factors.

Example 6

Factor 242 - 44x - 40.

Solution We an initial factor 4 from each term to get

4(6x2 - 11x - 10)

We then element the trinomial, come obtain

4(3x + 2)(2x - 5)

ALTERNATIVE an approach OF FACTORING TRINOMIALS

If the over "trial and also error" method of factoring does not yield fast results, analternative method, i beg your pardon we will certainly now demonstrate using the earlier example4x2 + 8x + 3, might be helpful.

We know that the trinomial is factorable due to the fact that we discovered two numbers whoseproduct is 12 and whose sum is 8. Those numbers are 2 and also 6. We now proceedand use these number to rewrite 8x together 2x + 6x. We now factor the very first two terms, 4*2 + 2x and also the last 2 terms, 6x + 3.A usual factor, 2x + 1, is in each term, so we can factor again.This is the same result that we obtained before.

## 4.7FACTORING THE distinction OF 2 SQUARES

Some polynomials happen so frequently that the is valuable to acknowledge these specialforms, i beg your pardon in tum allows us to directly write your factored form. Watch that In this ar we room interested in city hall this connection from right to left, fromthe polynomial a2 - b2 come its factored form (a + b)(a - b).

The difference of two squares, a2 - b2, equates to the product that the amount a + b and also the difference a - b.

Example 1

a. X2 - 9 = x2 - 32 = (x + 3)(x - 3) b. X2 - 16 = x2 - 42 = (x + 4)(x - 4)

Since

(3x)(3x) = 9x2

we deserve to view a binomial such as 9x2 - 4 as (3x)2 - 22 and also use the over methodto factor.

Example 2

a.9x2 - 4 = (3x)2 - 22= (3x + 2)(3x - 2)b.4y2 - 25x2 = (2y)2 - (5x)2= (2y + 5x)(2y - 5x)

As before, we always factor out a typical monomial very first whenever possible.

Example 3

a.x3 - x5 = x3(l - x2) = x3(1 + x)(l - x)b.a2x2y - 16y = y(a2x2 - 16) = y<(ax)2 - 42>= y(ax - 4 )(ax + 4)

## 4.8EQUATIONS entailing PARENTHESES

Often we have to solve equations in i m sorry the change occurs in ~ parentheses. Wecan deal with these equations in the usual manner after ~ we have simplified castle byapplying the distributive legislation to eliminate the parentheses.

Example 1

Solve 4(5 - y) + 3(2y - 1) = 3.

Solution We an initial apply the distributive law to get

20 - 4y + 6y - 3 = 3

Now combining prefer terms and also solving for y yields

2y + 17 = 3

2y = -14

y=-l

The same an approach can be used to equations including binomial products.

Example 2

Solve (x + 5)(x + 3) - x = x2 + 1.

Solution First, we apply the FOIL technique to eliminate parentheses and also obtain

x2 + 8x + 15 - x = x2 + 1

Now, combining favor terms and also solving because that x yields

x2 + 7x + 15 = x2 + 1

7x = -14

x = -2

## 4.9WORD problems INVOLVING NUMBERS

Parentheses are useful in representing commodities in i m sorry the change is containedin one or more terms in any factor.

Example 1

One integer is three an ext than another. If x represents the smaller integer, representin terms of x

a. The larger integer.b. Five times the smaller sized integer.c. 5 times the larger integer.

Solution a. X + 3b. 5x c. 5(x + 3)

Let united state say we recognize the sum of 2 numbers is 10. If we stand for one number byx, climate the second number must be 10 - x as argued by the complying with table. In general, if we understand the amount of 2 numbers is 5 and also x to represent one number,the various other number must be S - x.

Example 2

The amount of two integers is 13. If x to represent the smaller sized integer, represent in termsof X

a. The larger integer.b. Five times the smaller sized integer.c. Five times the larger integer.

Solution a. 13 - x b. 5x c. 5(13 - x)

The next example pertains to the concept of consecutive integers the was consid-ered in ar 3.8.

Example 3

The difference of the squares of two consecutive weird integers is 24. If x representsthe smaller integer, stand for in terms of x

a. The bigger integerb. The square that the smaller integer c. The square the the larger integer.

Solution

a. X + 2b. X2 c. (x + 2)2

Sometimes, the math models (equations) because that word difficulties involveparentheses. We deserve to use the technique outlined on page 115 to achieve the equation.Then, we proceed to resolve the equation by an initial writing equivalently the equationwithout parentheses.

Example 4

One essence is five more than a second integer. Three times the smaller sized integer plustwice the larger equals 45. Find the integers.

Solution

Steps 1-2 First, we write what we want to discover (the integers) together word phrases. Then, we stand for the integers in regards to a variable.The smaller sized integer: x The larger integer: x + 5

Step 3 A map out is not applicable.

Step 4 Now, we compose an equation that represents the condition in the problemand get

3x + 2(x + 5) = 45

Step 5 using the distributive law to eliminate parentheses yields Step 6 The integers room 7 and 7 + 5 or 12.

## 4.10 APPLICATIONS

In this section, we will examine several applications the word difficulties that lead toequations the involve parentheses. When again, we will certainly follow the six measures out-lined on web page 115 once we settle the problems.

COIN PROBLEMS

The simple idea of problems involving coins (or bills) is the the value of a numberof coins that the same denomination is same to the product of the value of a singlecoin and the total number of coins. A table favor the one displayed in the next instance is beneficial in resolving coin problems.

Example 1

A repertoire of coins consisting of dimes and also quarters has actually a worth of \$5.80. Thereare 16 much more dimes than quarters. How countless dimes and quarters room in the col-lection?

Solution

Steps 1-2 We very first write what we desire to discover as indigenous phrases. Then, werepresent each expression in regards to a variable.The variety of quarters: x The variety of dimes: x + 16

Step 3 Next, us make a table mirroring the variety of coins and their value. Step 4 now we have the right to write one equation. Step 5 resolving the equation yields Step 6 There are 12 quarters and also 12 + 16 or 28 dimes in the collection.

INTEREST PROBLEMS

The an easy idea of fixing interest problems is that the quantity of attention i earnedin one year at straightforward interest amounts to the product that the rate of attention r and also theamount that money p invested (i = r * p). For example, \$1000 invested because that one yearat 9% returns i = (0.09)(1000) = \$90.

A table choose the one shown in the next example is beneficial in fixing interestproblems.

Example 2

Two investments produce an yearly interest that \$320. \$1000 more is invested at11% than at 10%. Just how much is invested at every rate?

Solution

Steps 1-2 We first write what we desire to discover as word phrases. Then, werepresent each expression in regards to a variable. Amount invest at 10%: x Amount invest at 11%: x + 100

Step 3 Next, we make a table reflecting the amount of money invested, therates of interest, and the amounts of interest. Step 4 Now, we deserve to write an equation relating the attention from every in-vestment and the full interest received. Step 5 To deal with for x, an initial multiply each member by 100 to obtain Step 6 \$1000 is invested at 10%; \$1000 + \$1000, or \$2000, is invest at11%.

MIXTURE PROBLEMS

The simple idea of addressing mixture problems is the the amount (or value) that thesubstances being blended must same the amount (or value) of the final mixture.

A table like the ones displayed in the following examples is valuable in solvingmixture problems.

Example 3

How lot candy worth 80c a kilogram (kg) need to a grocer blend with 60 kg ofcandy precious \$1 a kilogram to do a mixture worth 900 a kilogram?

Solution

Steps 1-2 We very first write what we want to uncover as a word phrase. Then, werepresent the expression in terms of a variable.Kilograms of 80c candy: x

Step 3 Next, us make a table showing the species of candy, the lot of each,and the full values the each. Step 4 We deserve to now write an equation. Step 5 solving the equation yields Step 6 The grocer must use 60 kg the the 800 candy.

Another kind of mixture problem is one that requires the mixture the the 2 liquids.

Example 4

How numerous quarts that a 20% equipment of acid need to be added to 10 quarts the a 30%solution of acid to acquire a 25% solution?

Solution

Steps 1-2 We an initial write what we want to uncover as a indigenous phrase. Then, werepresent the phrase in regards to a variable.

Number that quarts of 20% systems to it is in added: x

Step 3 Next, we make a table or illustration showing the percent of every solu-tion, the quantity of each solution, and also the quantity of pure mountain in eachsolution.  Step 4 We have the right to now write an equation relating the quantities of pure mountain beforeand after combine the solutions. Step 5 To settle for x, very first multiply each member by 100 come obtain

20x + 30(10) = 25(x + 10)20x + 300 = 25x + 250 50 = 5x 10 = x

Step 6 add 10 quarts that 20% equipment to produce the preferred solution.

## CHAPTER SUMMARY

Algebraic expressions containing parentheses can be composed without clip byapplying the distributive legislation in the forma(b + c) = abdominal muscle + ac

A polynomial that includes a monomial factor usual to every terms in thepolynomial can be written as the product that the typical factor and also anotherpolynomial by applying the distributive regulation in the formab + ac = a(b + c)

The distributive law have the right to be supplied to multiply binomials; the FOIL method suggeststhe four assets involved. Given a trinomial that the kind x2 + Bx + C, if there room two numbers, a and b,whose product is C and also whose amount is B, then x2 + Bx + C = (x + a)(x + b) otherwise, the trinomial is no factorable.

A trinomial of the form Ax2 + Bx + C is factorable if there are two number whoseproduct is A * C and whose sum is B.

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The distinction of squaresa2 - b2 = (a + b)(a - b)

Equations involving parentheses can be fixed in the usual method after the equationhas to be rewritten equivalently there is no parentheses.