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6.1: Exponents rules and properties

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Definition

If a is a positive real number and n is any real number, then in an, a is called the base and n is called the exponent.

Note

When the directions state simplify, this means

  • All exponents are positive
  • Each base only occurs once
  • There are no parenthesis
  • There are no powers written to powers

Product Rule of Exponents

Let’s take a look at an example with multiplication.

Example 6.1.1

Simplify: a3a2

Solution

First, let’s rewrite this product in expanded form and then combine with one base a.

a3a2Expand(aaa)(aa)Rewrite with one base aaaaaa5 timesMultiplying a five timesa5Simplified expression

Let’s think about Example 6.1.1 . This method of expanding seems to be fine when there are smaller exponents, but what if we were given something like a100a934? Are we going to expand a over a thousand times? No way! We need a more sophisticated way in multiplying expressions with exponents. Hence, taking a look at Example 6.1.1 , we can see the result is a5. Notice we could have obtained this answer without expanding but by simply adding the exponents:

a3a2=a3+2=a5

This is called the product rule of exponents.

Product Rule for Exponents

Let a be a positive real number and n and m be any real number. Then anam=an+m

Note

In order to add exponents, the bases of the factors are required to be the same.

Example 6.1.2

Simplify: 32363

Solution

Let’s apply the product rule and simplify. Don’t forget that 3 has an exponent, it is one: 31.

We don’t always write it, but we know it’s there.

323631Same base32+6+1Add the exponents39Simplified expression

We can simplify this even more as 19,683 (39=19683).

Example 6.1.3

Simplify: (2x3y5z)(5xy2z3)

Solution

(2x3y5z)(5xy2z3)Rewrite without parenthesis2x3y5z15x1y2z3Multiply the coefficients and add exponents with same bases25x3+1y5+2z1+3Add exponents and multiply the coefficients10x4y7z4Simplified expression

Quotient Rule of Exponents

Example 6.1.4

Simplify: a5a2

Solution

a5a2ExpandaaaaaaaReduce the common factorsaaaaaaaSimplifyaaaRewrite with one base aa3Simplified expression

Let’s think about Example 6.1.4 . This method of expanding seems to be fine when there are smaller exponents, but what if we were given something like a199a827? Are we going to expand a over a thousand times? No way! We need a more sophisticated way in dividing expressions with exponents. Hence, taking a look at Example 6.1.4 , we can see the result is a3. Notice we could have obtained this answer without expanding but by simply subtracting the exponents:

a5a2=a52=a3

This is called the quotient rule of exponents.

Quotient Rule for Exponents

Let a be a positive real number and n and m be any real number. Then anam=anm

Note

In order to subtract exponents, the bases of the dividend and divisor are required to be the same. Be sure that the denominator exponent is subtracted from the numerator exponent.

Example 6.1.5

Simplify: 71375

Solution

71375Same base7135Subtract exponents78Simplified expression

We can simplify this even more as 5,764,801 (78=5764801).

Example 6.1.6

Simplify: 5a3b5c22ab3c

Solution

5a3b5c22a1b3c1Subtract exponents with same bases and simplify coefficients, if possible5a31b53c212Simplify5a2b2c2Simplified expression

We could also write the expression with the fraction as a coefficient: 52a2b2c. These are equivalent and both correct.

Power Rule of Exponents

Example 6.1.7

Simplify: (a2)3

Solution

First, let’s rewrite this expression in expanded form and then combine with one base a.

(a2)3Expanda2a2a2Apply the product rulea2+2+2Add exponentsa6Simplified expression

Let’s think about Example 6.1.7 . This method of expanding seems to be fine when there are smaller exponents, but what if we were given something like (a760)34? Are we going to expand a over a twenty-thousand times? No way! We need a more sophisticated way in simplifying expressions with exponents raised to exponents. Hence, taking a look at Example 6.1.7 , we can see the result is a6. Notice we could have obtained this answer without expanding but by simply multiplying the exponents:

(a2)3=a23=a6

This is called the power rule of exponents.

Power Rule for Exponents

Let a be a positive real number and n and m be any real number. Then (an)m=amn

Furthermore, we can extend the power rule for when we have more than one factor in the base.

Example 6.1.8

Simplify: (ab)3

Solution

We can expand the base, then rewrite with one base of a and b.

(ab)3Expand(ab)(ab)(ab)Let's rewrite this grouping a's and b'saaabbbRewrite with one base of a and ba3b3Simplified expression

Let’s think about Example 6.1.8 . This method of expanding seems to be fine when there are smaller exponents, but what if we were given something like (ab)2049? Are we going to expand a and b over a two-thousand times? No way! We need a more sophisticated way in simplifying expressions with exponents raised to exponents with more than one factor in the base. Hence, taking a look at Example 6.1.8 , we can see the result is a3b3. Notice we could have obtained this answer without expanding but by simply applying the exponent to each factor in the base:

(ab)3=a3b3=a3b3

This is called the power of a product rule (POP).

Power of a Product Rule (POP)

Let a and b be a positive real numbers and n be any real number. Then (ab)n=anbm

Note

It is important to be careful to only use the power of a product rule with multiplication inside parenthesis. This property is not allowed for addition or subtraction, i.e., (a+b)mam+bm

Example 6.1.9

Simplify: (ab)3

Solution

Let’s expand the fraction and rewrite with one base of a and b.

(ab)3Expand(ab)(ab)(ab)Multiply fractionsa3b3Simplified expression

Notice, this is similar to the POP rule and we can apply the exponent to each numerator and denominator.

Power of a Quotient Rule

Let a and b be a positive real numbers and n be any real number. Then (ab)n=anbn

Let’s look at an example where we have to combine all these exponent rules.

Example 6.1.10

Simplify: (x3yz2)4

Solution

(x3y1z2)4Apply the POP rulex34y14z24Multiply exponentsx12y4z8Simplified expression

Example 6.1.11

Simplify: (a3bc8d5)2

Solution

(a3b1c8d5)2Apply the power of a quotient rulea32b12c82d52Multiply exponentsa6b2c16d10Simplified expression

Example 6.1.12

Simplify: (4x2y5)3

Solution

(41x2y5)3Apply the POP rule431x23y53Multiply exponents43x6y15Evaluate 4364x6y15Simplified expression

Notice that the exponent also applied to the coefficient 4 and we had to evaluate 43=64 as part of the expression.

Exponent Rules

Let a and b be positive real numbers and n and m be any real numbers.

Rule 1. anam=an+m

Rule 2. anam=anm

Rule 3. (an)m=anm

Rule 4. (ab)n=anbn

Rule 5. (ab)n=anbn

Zero as an Exponent

Here we discuss zero as an exponent. This is one of two cases where the exponent isn’t positive. The other case is where the exponents are negative, but we will save that for the next section. Let’s look an example:

Example 6.1.13

Simplify: a3a3

Solution

If we applied the quotient rule right away, we would get

a3a3=a33=a0

But what does this mean? What is a0? Well, let’s take a look at this same example with a different approach:

a3a3ExpandaaaaaaReduce common factors of aaaaaaaSimplify11Simplify1Simplified expression

If a3a3=a0 from the first part and a3a3=1 from the second part, then this implies a0=1.

Zero Power Rule

Let a be a positive real number. Then a0=1, i.e., any positive real number to the power of zero is 1.

Example 6.1.14

Simplify: (3x2)0

Solution

Since 3x2 is raised to the power of zero, then we can apply the zero power rule:

(3x2)0Zero power rule1Simplified expression

Negative Exponents

Another property we consider is expressions with negative exponents.

Example 6.1.15

Simplify: a3a5

Solution

If we applied the quotient rule right away, we would get

a3a5=a35=a2

But what does this mean? What is a2? Well, let’s take a look at this same example with a different approach:

a3a5ExpandaaaaaaaaReduce common factors of aaaaaaaaaSimplify1aaSimplify1a2Simplified expession

If a3a5=a2 from the first part and a3a5=1a2 from the second part, then this implies a2=1a2.

This example illustrates an important property of exponents. Negative exponents yield the reciprocal of the base. Once we take the reciprocal, the exponent is now positive.

Note

It is important to note a negative exponent does not imply the expression is negative, only the reciprocal of the base. Hence, negative exponents imply reciprocals.

Also, recall the rules of simplifying:

  • All exponents are positive
  • Each base only occurs once
  • There are no parenthesis
  • There are no powers written to powers

This includes rewriting all negative exponents as positive exponents.

Negative Exponents Rules

Let a and b be positive real numbers and n be any real number.

Rule 1. an=1an

Rule 2. 1an=an

Rule 3. (ab)n=(ba)n

Negative exponents are combined in several different ways. As a general rule, in a fraction, a base with a negative exponent moves to the other side of the fraction bar as the exponent changes sign.

Example 6.1.16

Simplify: a3b2c2d1e4f2

Solution

We can rewrite the expression with positive exponents using the rules of exponents:

a3b2c2d1e4f2Reciprocate the terms with negative exponentsa3cde42b2f2Simplified expression

As we simplified the fraction, we took special care to move each base that had a negative exponent, but the expression itself did not become negative. Also, it is important to remember that exponents only effect the base. The 2 in the denominator has an exponent of one (we don’t always write it, but we know it’s there), so it does not move with the d.

Note

Nicolas Chuquet, the French mathematician of the 15th century wrote 121¯m to indicate 12x1. This was the first known use of the negative exponent.

Properties of Exponents

Putting all the rules together, we can simplify more complex expression containing exponents. Here we apply all the rules of exponents to simplify expressions.

General Exponent Rules

Let a and b be positive real numbers and n and m be any real numbers.

Rule 1. anam=an+m

Rule 2. anam=anm

Rule 3. (an)m=anm

Rule 4. (ab)n=anbn

Rule 5. (ab)n=anbn

Rule 6. a0=1

Rule 7. an=1an

Rule 8. 1an=an

Rule 9. (ab)n=(ba)n

Example 6.1.17

Simplify: 4x5y33x3y26x5y3

Solution

4x5y33x3y26x5y3Simplify the numerator by applying the product rule12x2y56x5y3Simplify by applying the quotient rule126x2(5)y53Simplify2x3y8Rewrite with only positive exponents2x3y8Simplified expression

Example 6.1.18

Simplify: (3ab3)2ab32a4b0

Solution

(3ab3)2a1b32a4b0Apply POP and zero power rule32a2b6a1b32a41Apply product rule32a1b92a4Apply the quotient rule32a3b92Rewrite with only positive exponentsa3232b9Simplifya318b9Simplified expression

It is important to point out that when we simplified 32, we moved the 32 to the denominator and the exponent became positive. We did not make the number negative. Negative exponents never make the bases negative; they simply mean we have to take the reciprocal of the base.

Example 6.1.19

Simplify: (3x2y5z36x6y2z39(x2y2)3)3

Solution

This example looks more involved that any of the other examples, but we will apply the same method. It is advised, in these types of problems, that we simplify the expression inside the parenthesis first, and then apply the POP rule. We even should start with simplifying each numerator and denoinator before simplifying the fraction with the quotient rule.

(3x2y5z36x6y2z39(x2y2)3)3Simplify each numeratr and denominator(18x8y3z09x6y6)3Apply the quotient rule(2x2y3z0)3Apply the POP rule23x6y9z0Rewrite only with positive exponentsx6y923Simplifyx6y98Simplified expression

Exponent Rules and Properties Homework

Simplify. Be sure to follow the simplifying rules and write answers with positive exponents.

Exercise 6.1.1

44444

Exercise 6.1.2

422

Exercise 6.1.3

3m3mn

Exercise 6.1.4

2m4n24nm2

Exercise 6.1.5

(33)4

Exercise 6.1.6

(44)2

Exercise 6.1.7

(2u3v2)2

Exercise 6.1.8

(2a4)4

Exercise 6.1.9

4543

Exercise 6.1.10

323

Exercise 6.1.11

3nm23n

Exercise 6.1.12

4x3y43xy3

Exercise 6.1.13

(x3y42x2y3)2

Exercise 6.1.14

2x(x4y4)4

Exercise 6.1.15

2x7y53x3y4x2y3

Exercise 6.1.16

((2x)3x3)2

Exercise 6.1.17

(2y17(2x2y4)4)3

Exercise 6.1.18

(2mn42m4n4mn4)3

Exercise 6.1.19

2xy52x2y32xy4y3

Exercise 6.1.20

q3r2(2p2q2r3)22p3

Exercise 6.1.21

(zy3z3x4y4x3y3z3)4

Exercise 6.1.22

2x2y2z62zx2y2(x2z3)2

Exercise 6.1.23

44442

Exercise 6.1.24

33332

Exercise 6.1.25

3x4x2

Exercise 6.1.26

x2y4xy2

Exercise 6.1.27

(43)4

Exercise 6.1.28

(32)3

Exercise 6.1.29

(xy)3

Exercise 6.1.30

(2xy)4

Exercise 6.1.31

3733

Exercise 6.1.32

343

Exercise 6.1.33

x2y44xy

Exercise 6.1.34

xy34xy

Exercise 6.1.35

(u2v22u4)3

Exercise 6.1.36

3vu52v3uv22u3v

Exercise 6.1.37

2ba72b4ba23a3b4

Exercise 6.1.38

2a2b2a7(ba4)2

Exercise 6.1.39

yx2(y4)22y4

Exercise 6.1.40

n3(n4)22mn

Exercise 6.1.41

(2y3x2)22x2y4x2

Exercise 6.1.42

2x4y52z10x2y7(xy2z2)4

Exercise 6.1.43

(2q3p3r42p3(qrp3)2)4

Exercise 6.1.44

2x4y2(2xy3)4

Exercise 6.1.45

(a4b3)32a3b2

Exercise 6.1.46

(2x2y2)4x4

Exercise 6.1.47

(x3y4)3x4y4

Exercise 6.1.48

2x3y23x3y33x0

Exercise 6.1.49

4xy3x4y04y1

Exercise 6.1.50

u2v12u0v42uv

Exercise 6.1.51

u24u0v33v2

Exercise 6.1.52

2y(x0y2)4

Exercise 6.1.53

(2a2b3a1)4

Exercise 6.1.54

2nm4(2m2n2)4

Exercise 6.1.55

(2mn)4m0n2

Exercise 6.1.56

y3x3y2(x4y2)3

Exercise 6.1.57

2u2v3(2uv4)12u4v0

Exercise 6.1.58

(2x0y4y4)3

Exercise 6.1.59

y(2x4y2)22x4y0

Exercise 6.1.60

2yzx22x4y4z2(zy2)4

Exercise 6.1.61

2kh02h3k0(2kj3)2

Exercise 6.1.62

(cb3)22a3b2(a3b2c3)3

Exercise 6.1.63

(yx4z2)1z3x2y3z1

Exercise 6.1.64

2a2b3(2a0b4)4

Exercise 6.1.65

2x3y2(2x3)0

Exercise 6.1.66

(m0n32m3n3)0

Exercise 6.1.67

2m1n3(2m1n3)4

Exercise 6.1.68

3y33yx32x4y3

Exercise 6.1.69

3x3y24y23x2y4

Exercise 6.1.70

2xy24x3y44x4y44x

Exercise 6.1.71

2x2y24yx2

Exercise 6.1.72

(a4)42b

Exercise 6.1.73

(2y4x2)2

Exercise 6.1.74

2y2(x4y0)4

Exercise 6.1.75

2x3(x4y3)1

Exercise 6.1.76

2x2y02xy4(xy0)1

Exercise 6.1.77

2yx2x2(2x0y4)1

Exercise 6.1.78

u3v42v(2u3v4)0

Exercise 6.1.79

b1(2a4b0)02a3b2

Exercise 6.1.80

2b4c2(2b3c2)4a2b4

Exercise 6.1.81

((2x3y0z1)3x3y22x3)2

Exercise 6.1.82

2q4m2p2q4(2m4p2)3

Exercise 6.1.83

2mpn3(m0n4p2)32n2p0


This page titled 6.1: Exponents rules and properties is shared under a CC BY-NC-SA 4.0 license and was authored, remixed, and/or curated by Darlene Diaz (ASCCC Open Educational Resources Initiative) via source content that was edited to the style and standards of the LibreTexts platform.

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