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6.5 Divide Monomials

Simplify Expressions Using the Quotient Property for Exponents

Earlier in this chapter, we developed the properties of exponents for multiplication. We summarize these properties below.

Now we will look at the exponent properties for division. A quick memory refresher may help before we get started. You have learned to simplify fractions by dividing out common factors from the numerator and denominator using the Equivalent Fractions Property. This property will also help you work with algebraic fractions—which are also quotients.

As before, we’ll try to discover a property by looking at some examples.

Considerx5x2andx2x3
What do they mean?x·x·x·x·xx·xx·xx·x·x
Use the Equivalent Fractions Property.x·x·x·x·xx·xx·x·1x·x·x
Simplify.x31x

Notice, in each case the bases were the same and we subtracted exponents.

When the larger exponent was in the numerator, we were left with factors in the numerator.

When the larger exponent was in the denominator, we were left with factors in the denominator—notice the numerator of 1.

We write:

x5x2x2x3x521x32x31x

This leads to the Quotient Property for Exponents.

A couple of examples with numbers may help to verify this property.

3432=3425253=1532819=3225125=1519=915=15

Notice the difference in the two previous examples:

  • If we start with more factors in the numerator, we will end up with factors in the numerator.
  • If we start with more factors in the denominator, we will end up with factors in the denominator.

The first step in simplifying an expression using the Quotient Property for Exponents is to determine whether the exponent is larger in the numerator or the denominator.

Simplify Expressions with an Exponent of Zero

A special case of the Quotient Property is when the exponents of the numerator and denominator are equal, such as an expression like amam. From your earlier work with fractions, you know that:

22=11717=1−43−43=1

In words, a number divided by itself is 1. So, xx=1, for any x(x0), since any number divided by itself is 1.

The Quotient Property for Exponents shows us how to simplify aman when m>n and when n<m by subtracting exponents. What if m=n?

Consider 88, which we know is 1.

88=1
Write 8 as 23.2323=1
Subtract exponents.233=1
Simplify.20=1

Now we will simplify amam in two ways to lead us to the definition of the zero exponent. In general, for a0:

This figure is divided into two columns. At the top of the figure, the left and right columns both contain a to the m power divided by a to the m power. In the next row, the left column contains a to the m minus m power. The right column contains the fraction m factors of a divided by m factors of a, represented in the numerator and denominator by a times a followed by an ellipsis. All the as in the numerator and denominator are canceled out. In the bottom row, the left column contains a to the zero power. The right column contains 1.

We see amam simplifies to a0 and to 1. So a0=1.

In this text, we assume any variable that we raise to the zero power is not zero.

Now that we have defined the zero exponent, we can expand all the Properties of Exponents to include whole number exponents.

What about raising an expression to the zero power? Let’s look at (2x)0. We can use the product to a power rule to rewrite this expression.

Table 6.1
(2x)0
Use the product to a power rule.20x0
Use the zero exponent property.1·1
Simplify.1

This tells us that any nonzero expression raised to the zero power is one.

Simplify Expressions Using the Quotient to a Power Property

Now we will look at an example that will lead us to the Quotient to a Power Property.

(xy)3
This means:xy·xy·xy
Multiply the fractions.x·x·xy·y·y
Write with exponents.x3y3

Notice that the exponent applies to both the numerator and the denominator.

We write:(xy)3
x3y3

This leads to the Quotient to a Power Property for Exponents.

An example with numbers may help you understand this property:

(23)3=233323·23·23=827827=827

Simplify Expressions by Applying Several Properties

We’ll now summarize all the properties of exponents so they are all together to refer to as we simplify expressions using several properties. Notice that they are now defined for whole number exponents.

Divide Monomials

You have now been introduced to all the properties of exponents and used them to simplify expressions. Next, you’ll see how to use these properties to divide monomials. Later, you’ll use them to divide polynomials.

Once you become familiar with the process and have practiced it step by step several times, you may be able to simplify a fraction in one step.

In all examples so far, there was no work to do in the numerator or denominator before simplifying the fraction. In the next example, we’ll first find the product of two monomials in the numerator before we simplify the fraction. This follows the order of operations. Remember, a fraction bar is a grouping symbol.

Key Concepts

  • Quotient Property for Exponents:
    • If a is a real number, a0, and m,n are whole numbers, then:
      aman=amn,m>nandaman=1amn,n>m
  • Zero Exponent
    • If a is a non-zero number, then a0=1.

  • Quotient to a Power Property for Exponents:
    • If a and b are real numbers, b0, and m is a counting number, then:
      (ab)m=ambm
    • To raise a fraction to a power, raise the numerator and denominator to that power.

  • Summary of Exponent Properties
    • If a,b are real numbers and m,n are whole numbers, then
      Product Propertyam·an=am+nPower Property(am)n=am·nProduct to a Power(ab)m=ambmQuotient Propertyaman=amn,a0,m>naman=1anm,a0,n>mZero Exponent Definitionao=1,a0Quotient to a Power Property(ab)m=ambm,b0

Practice Makes Perfect

Simplify Expressions Using the Quotient Property for Exponents

In the following exercises, simplify.

x18x351253

y20y1071672

y10714

p21p741644

u24u391595

u21910

q18q36102103

t10t408385

1t30164

bb9446

xx710103

1x61100

Simplify Expressions with Zero Exponents

In the following exercises, simplify.

200b0

130k0

ⓐ 1 ⓑ 1

270(270)

150(150)

−1−1

(25x)025x0

(6y)06y0

ⓐ 1 ⓑ 6

(12x)0(−56p4q3)0

7y0(17y)0(−93c7d15)0

ⓐ 7 ⓑ 1

12n018m0(12n)0(18m)0

15r022s0(15r)0(22s)0

−7 ⓑ 0

Simplify Expressions Using the Quotient to a Power Property

In the following exercises, simplify.

(34)3(p2)5(xy)6

(25)2(x3)4(ab)5

425x481a5b5

(a3b)4(54m)2

(x2y)3(103q)4

x38y310,00081q4

Simplify Expressions by Applying Several Properties

In the following exercises, simplify.

(a2)3a4

(p3)4p5

p7

(y3)4y10

(x4)5x15

x5

u6(u3)2

v20(v4)5

1

m12(m8)3

n8(n6)4

1n16

(p9p3)5

(q8q2)3

q18

(r2r6)3

(m4m7)4

1m12

(pr11)2

(ab6)3

a3b18

(w5x3)8

(y4z10)5

y20z50

(2j33k)4

(3m55n)3

27m15125n3

(3c24d6)3

(5u72v3)4

625u2816v12

(k2k8k3)2

(j2j5j4)3

j9

(t2)5(t4)2(t3)7

(q3)6(q2)3(q4)8

1q8

(−2p2)4(3p4)2(−6p3)2

(−2k3)2(6k2)4(9k4)2

64k6

(−4m3)2(5m4)3(−10m6)3

(−10n2)3(4n5)2(2n8)2

−4,000

Divide Monomials

In the following exercises, divide the monomials.

56b8÷ 7b2

63v10÷ 9v2

7v8

−88y15÷ 8y3

−72u12÷ 12u4

−6u8

45a6b8−15a10b2

54x9y3−18x6y15

3x3y12

15r4s918r9s2

20m8n430m5n9

2m33n5

18a4b8−27a9b5

45x5y9−60x8y6

−3y34x3

64q11r9s348q6r8s5

65a10b8c542a7b6c8

65a3b242c3

(10m5n4)(5m3n6)25m7n5

(−18p4q7)(−6p3q8)−36p12q10

−3q5p5

(6a4b3)(4ab5)(12a2b)(a3b)

(4u2v5)(15u3v)(12u3v)(u4v)

5v4u2

Mixed Practice

24a5+2a524a52a524a5·2a524a5÷2a5

15n10+3n1015n103n1015n10·3n1015n10÷3n10

18n1012n1045n20 ⓓ 5

p4·p6(p4)6

q5·q3(q5)3

q8q15

y3yyy3

z6z5z5z6

z1z

(8x5)(9x)÷6x3

(4y)(12y7)÷8y2

6y6

27a73a3+54a99a5

32c114c5+42c96c3

15c6

32y58y260y105y7

48x66x435x97x7

3x2

63r6s39r4s272r2s26s

56y4z57y3z345y2z25y

yz2

Everyday Math

Memory One megabyte is approximately 106 bytes. One gigabyte is approximately 109 bytes. How many megabytes are in one gigabyte?

Memory One gigabyte is approximately 109 bytes. One terabyte is approximately 1012 bytes. How many gigabytes are in one terabyte?

103

Writing Exercises

Jennifer thinks the quotient a24a6 simplifies to a4. What is wrong with her reasoning?

Maurice simplifies the quotient d7d by writing d7d=7. What is wrong with his reasoning?

Answers will vary.

When Drake simplified 30 and (−3)0 he got the same answer. Explain how using the Order of Operations correctly gives different answers.

Robert thinks x0 simplifies to 0. What would you say to convince Robert he is wrong?

Answers will vary.

Self Check

ⓐ After completing the exercises, use this checklist to evaluate your mastery of the objectives of this section.

This is a table that has six rows and four columns. In the first row, which is a header row, the cells read from left to right “I can…,” “Confidently,” “With some help,” and “No-I don’t get it!” The first column below “I can…” reads “simplify expressions using the Quotient Property for Exponents,” “simplify expressions with zero exponents,” “simplify expressions using the Quotient to a Power Property,” “simplify expressions by applying several properties,” and “divide monomials.” The rest of the cells are blank.

ⓑ On a scale of 1-10, how would you rate your mastery of this section in light of your responses on the checklist? How can you improve this?