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Study Guides > Prealgebra

Simplifying Expressions With Negative Exponents

Learning Outcomes

  • Use the properties of exponents to simplify products and quotients that contain negative exponents and variables
  All the exponent properties we developed earlier in this chapter with whole number exponents apply to integer exponents, too. We restate them here for reference.

Summary of Exponent Properties

If a,ba,b are real numbers and m,nm,n are integers, then Product Propertyaman=am+nPower Property(am)n=amnProduct to a Power Property(ab)m=ambmQuotient Propertyaman=amn,a0Zero Exponent Propertya0=1,a0Quotient to a Power Property(ab)m=ambm,b0Definition of Negative Exponentan=1an\begin{array}{cccc}\mathbf{\text{Product Property}}\hfill & & & {a}^{m}\cdot {a}^{n}={a}^{m+n}\hfill \\ \mathbf{\text{Power Property}}\hfill & & & {\left({a}^{m}\right)}^{n}={a}^{m\cdot n}\hfill \\ \mathbf{\text{Product to a Power Property}}\hfill & & & {\left(ab\right)}^{m}={a}^{m}{b}^{m}\hfill \\ \mathbf{\text{Quotient Property}}\hfill & & & \frac{{a}^{m}}{{a}^{n}}={a}^{m-n},a\ne 0\hfill \\ \mathbf{\text{Zero Exponent Property}}\hfill & & & {a}^{0}=1,a\ne 0\hfill \\ \mathbf{\text{Quotient to a Power Property}}\hfill & & & {\left(\frac{a}{b}\right)}^{m}=\frac{{a}^{m}}{{b}^{m}},b\ne 0\hfill \\ \mathbf{\text{Definition of Negative Exponent}}\hfill & & & {a}^{-n}=\frac{1}{{a}^{n}}\hfill \end{array}
 

example

Simplify: 1. x4x6{x}^{-4}\cdot {x}^{6} 2. y6y4{y}^{-6}\cdot {y}^{4} 3. z5z3{z}^{-5}\cdot {z}^{-3} Solution
1.
x4x6{x}^{-4}\cdot {x}^{6}
Use the Product Property, aman=am+n{a}^{m}\cdot {a}^{n}={a}^{m+n}. x4+6{x}^{-4+6}
Simplify. x2{x}^{2}
2.
y6y4{y}^{-6}\cdot {y}^{4}
The bases are the same, so add the exponents. y6+4{y}^{-6+4}
Simplify. y2{y}^{-2}
Use the definition of a negative exponent, an=1an{a}^{-n}=\frac{1}{{a}^{n}}. 1y2\frac{1}{{y}^{2}}
3.
z5z3{z}^{-5}\cdot {z}^{-3}
The bases are the same, so add the exponents. z53{z}^{-5 - 3}
Simplify. z8{z}^{-8}
Use the definition of a negative exponent, an=1an{a}^{-n}=\frac{1}{{a}^{n}}. 1z8\frac{1}{{z}^{8}}
 

try it

[ohm_question]146301[/ohm_question]
    In the next two examples, we’ll start by using the Commutative Property to group the same variables together. This makes it easier to identify the like bases before using the Product Property of Exponents.  

example

Simplify: (m4n3)(m5n2)\left({m}^{4}{n}^{-3}\right)\left({m}^{-5}{n}^{-2}\right).

Answer: Solution

(m4n3)(m5n2)\left({m}^{4}{n}^{-3}\right)\left({m}^{-5}{n}^{-2}\right)
Use the Commutative Property to get like bases together. m4m5n2n3{m}^{4}{m}^{-5}\cdot {n}^{-2}{n}^{-3}
Add the exponents for each base. m1n5{m}^{-1}\cdot {n}^{-5}
Take reciprocals and change the signs of the exponents. 1m11n5\frac{1}{{m}^{1}}\cdot \frac{1}{{n}^{5}}
Simplify. 1mn5\frac{1}{m{n}^{5}}

 

try it

[ohm_question]146303[/ohm_question]
  If the monomials have numerical coefficients, we multiply the coefficients, just as we did in Integer Exponents and Scientific Notation.  

example

Simplify: (2x6y8)(5x5y3)\left(2{x}^{-6}{y}^{8}\right)\left(-5{x}^{5}{y}^{-3}\right).

Answer: Solution

(2x6y8)(5x5y3)\left(2{x}^{-6}{y}^{8}\right)\left(-5{x}^{5}{y}^{-3}\right)
Rewrite with the like bases together. 2(5)(x6x5)(y8y3)2\left(-5\right)\cdot \left({x}^{-6}{x}^{5}\right)\cdot \left({y}^{8}{y}^{-3}\right)
Simplify. 10x1y5-10\cdot {x}^{-1}\cdot {y}^{5}
Use the definition of a negative exponent, an=1an{a}^{-n}=\frac{1}{{a}^{n}}. 101x1y5-10\cdot \frac{1}{{x}^{1}}\cdot {y}^{5}
Simplify. 10y5x\frac{-10{y}^{5}}{x}

 

try it

[ohm_question]146304[/ohm_question]
  In the next two examples, we’ll use the Power Property and the Product to a Power Property.  

example

Simplify: (k3)2{\left({k}^{3}\right)}^{-2}.

Answer: Solution

(k3)2{\left({k}^{3}\right)}^{-2}
Use the Product to a Power Property, (ab)m=ambm{\left(ab\right)}^{m}={a}^{m}{b}^{m}. k3(2){k}^{3\left(-2\right)}
Simplify. k6{k}^{-6}
Rewrite with a positive exponent. 1k6\frac{1}{{k}^{6}}

 

try it

[ohm_question]146306[/ohm_question]
   

example

Simplify: (5x3)2{\left(5{x}^{-3}\right)}^{2}.

Answer: Solution

(5x3)2{\left(5{x}^{-3}\right)}^{2}
Use the Product to a Power Property, (ab)m=ambm{\left(ab\right)}^{m}={a}^{m}{b}^{m}. 52(x3)2{5}^{2}{\left({x}^{-3}\right)}^{2}
Simplify 52{5}^{2} and multiply the exponents of xx using the Power Property, (am)n=amn{\left({a}^{m}\right)}^{n}={a}^{m\cdot n}. 25k625{k}^{-6}
Rewrite x6{x}^{-6} by using the definition of a negative exponent, an=1an{a}^{-n}=\frac{1}{{a}^{n}}. 251x625\cdot \frac{1}{{x}^{6}}
Simplify 25x6\frac{25}{{x}^{6}}

 

try it

[ohm_question]146307[/ohm_question]
In the following video we show another example of how to simplify a product that contains negative exponents. https://youtu.be/J9A-JlTXnsQ To simplify a fraction, we use the Quotient Property.  

example

Simplify: r5r4\frac{{r}^{5}}{{r}^{-4}}.

Answer: Solution

r5r4\frac{r^5}{r^{-4}}
Use the Quotient Property, aman=amn\frac{{a}^{m}}{{a}^{n}}={a}^{m-n} . r5(4){r}^{5-(\color{red}{-4})}
Be careful to subtract 5(4)5-(\color{red}{-4})
Simplify. 494^9

 

try it

[ohm_question]146308[/ohm_question]
In the next video we share more examples of simplifying a quotient with negative exponents. https://youtu.be/J5MrZbpaAGc

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