Learning Outcomes
- Simplify expressions with exponents equal to zero.
- Simplify expressions with negative exponents.
- Simplify exponential expressions.
Return to the quotient rule. We made the condition that [latex]m>n[/latex] so that the difference [latex]m-n[/latex] would never be zero or negative. What would happen if [latex]m=n[/latex]? In this case, we would use the zero exponent rule of exponents to simplify the expression to 1. To see how this is done, let us begin with an example.
[latex]\dfrac{t^{8}}{t^{8}}=\dfrac{\cancel{t^{8}}}{\cancel{t^{8}}}=1[/latex]
If we were to simplify the original expression using the quotient rule, we would have
If we equate the two answers, the result is [latex]{t}^{0}=1[/latex]. This is true for any nonzero real number, or any variable representing a real number.
The sole exception is the expression [latex]{0}^{0}[/latex]. This appears later in more advanced courses, but for now, we will consider the value to be undefined.
A General Note: The Zero Exponent Rule of Exponents
For any nonzero real number [latex]a[/latex], the zero exponent rule of exponents states that
using order of operations with fractions
When simplifying expressions with exponents, it is sometimes helpful to rely on the rule for multiplying fractions to separate the factors before doing work on them. For example, to simplify the expression [latex]\dfrac{5 a^m z^2}{a^mz}[/latex] using exponent rules, you may find it helpful to break the fraction up into a product of fractions, then simplify.
[latex]\dfrac{5 a^m z^2}{a^mz}\quad=\quad 5\cdot\dfrac{a^m}{a^m}\cdot\dfrac{z^2}{z} \quad=\quad 5 \cdot a^{m-m}\cdot z^{2-1}\quad=\quad 5\cdot a^0 \cdot z^1 \quad=\quad 5z[/latex]
Example: Using the Zero Exponent Rule
Simplify each expression using the zero exponent rule of exponents.
- [latex]\dfrac{{c}^{3}}{{c}^{3}}[/latex]
- [latex]\dfrac{-3{x}^{5}}{{x}^{5}}[/latex]
- [latex]\dfrac{{\left({j}^{2}k\right)}^{4}}{\left({j}^{2}k\right)\cdot {\left({j}^{2}k\right)}^{3}}[/latex]
- [latex]\dfrac{5{\left(r{s}^{2}\right)}^{2}}{{\left(r{s}^{2}\right)}^{2}}[/latex]
Try It
Simplify each expression using the zero exponent rule of exponents.
- [latex]\dfrac{{t}^{7}}{{t}^{7}}[/latex]
- [latex]\dfrac{{\left(d{e}^{2}\right)}^{11}}{2{\left(d{e}^{2}\right)}^{11}}[/latex]
- [latex]\dfrac{{w}^{4}\cdot {w}^{2}}{{w}^{6}}[/latex]
- [latex]\dfrac{{t}^{3}\cdot {t}^{4}}{{t}^{2}\cdot {t}^{5}}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=44120&theme=oea&iframe_resize_id=mom1
https://ohm.lumenlearning.com/multiembedq.php?id=7833&theme=oea&iframe_resize_id=mom1
In this video we show more examples of how to simplify expressions with zero exponents.
Using the Negative Rule of Exponents
Another useful result occurs if we relax the condition that [latex]m>n[/latex] in the quotient rule even further. For example, can we simplify [latex]\dfrac{{h}^{3}}{{h}^{5}}[/latex]? When [latex]m<n[/latex]—that is, where the difference [latex]m-n[/latex] is negative—we can use the negative rule of exponents to simplify the expression to its reciprocal.
Divide one exponential expression by another with a larger exponent. Use our example, [latex]\dfrac{{h}^{3}}{{h}^{5}}[/latex].
If we were to simplify the original expression using the quotient rule, we would have
Putting the answers together, we have [latex]{h}^{-2}=\dfrac{1}{{h}^{2}}[/latex]. This is true for any nonzero real number, or any variable representing a nonzero real number.
A factor with a negative exponent becomes the same factor with a positive exponent if it is moved across the fraction bar—from numerator to denominator or vice versa.
We have shown that the exponential expression [latex]{a}^{n}[/latex] is defined when [latex]n[/latex] is a natural number, 0, or the negative of a natural number. That means that [latex]{a}^{n}[/latex] is defined for any integer [latex]n[/latex]. Also, the product and quotient rules and all of the rules we will look at soon hold for any integer [latex]n[/latex].
A General Note: The Negative Rule of Exponents
For any nonzero real number [latex]a[/latex] and natural number [latex]n[/latex], the negative rule of exponents states that
Example: Using the Negative Exponent Rule
Write each of the following quotients with a single base. Do not simplify further. Write answers with positive exponents.
- [latex]\dfrac{{\theta }^{3}}{{\theta }^{10}}[/latex]
- [latex]\dfrac{{z}^{2}\cdot z}{{z}^{4}}[/latex]
- [latex]\dfrac{{\left(-5{t}^{3}\right)}^{4}}{{\left(-5{t}^{3}\right)}^{8}}[/latex]
Try It
Write each of the following quotients with a single base. Do not simplify further. Write answers with positive exponents.
- [latex]\dfrac{{\left(-3t\right)}^{2}}{{\left(-3t\right)}^{8}}[/latex]
- [latex]\dfrac{{f}^{47}}{{f}^{49}\cdot f}[/latex]
- [latex]\dfrac{2{k}^{4}}{5{k}^{7}}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=51959&theme=oea&iframe_resize_id=mom5
https://ohm.lumenlearning.com/multiembedq.php?id=109762&theme=oea&iframe_resize_id=mom10
https://ohm.lumenlearning.com/multiembedq.php?id=109765&theme=oea&iframe_resize_id=mom15
Watch this video to see more examples of simplifying expressions with negative exponents.
Example: Using the Product and Quotient Rules
Write each of the following products with a single base. Do not simplify further. Write answers with positive exponents.
- [latex]{b}^{2}\cdot {b}^{-8}[/latex]
- [latex]{\left(-x\right)}^{5}\cdot {\left(-x\right)}^{-5}[/latex]
- [latex]\dfrac{-7z}{{\left(-7z\right)}^{5}}[/latex]
Try It
Write each of the following products with a single base. Do not simplify further. Write answers with positive exponents.
- [latex]{t}^{-11}\cdot {t}^{6}[/latex]
- [latex]\dfrac{{25}^{12}}{{25}^{13}}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=93393&theme=oea&iframe_resize_id=mom20
Finding the Power of a Product
To simplify the power of a product of two exponential expressions, we can use the power of a product rule of exponents, which breaks up the power of a product of factors into the product of the powers of the factors. For instance, consider [latex]{\left(pq\right)}^{3}[/latex]. We begin by using the associative and commutative properties of multiplication to regroup the factors.
In other words, [latex]{\left(pq\right)}^{3}={p}^{3}\cdot {q}^{3}[/latex].
A General Note: The Power of a Product Rule of Exponents
For any real numbers [latex]a[/latex] and [latex]b[/latex] and any integer [latex]n[/latex], the power of a product rule of exponents states that
Example: Using the Power of a Product Rule
Simplify each of the following products as much as possible using the power of a product rule. Write answers with positive exponents.
- [latex]{\left(a{b}^{2}\right)}^{3}[/latex]
- [latex]{\left(2t\right)}^{15}[/latex]
- [latex]{\left(-2{w}^{3}\right)}^{3}[/latex]
- [latex]\dfrac{1}{{\left(-7z\right)}^{4}}[/latex]
- [latex]{\left({e}^{-2}{f}^{2}\right)}^{7}[/latex]
Try It
Simplify each of the following products as much as possible using the power of a product rule. Write answers with positive exponents.
- [latex]{\left({g}^{2}{h}^{3}\right)}^{5}[/latex]
- [latex]{\left(5t\right)}^{3}[/latex]
- [latex]{\left(-3{y}^{5}\right)}^{3}[/latex]
- [latex]\dfrac{1}{{\left({a}^{6}{b}^{7}\right)}^{3}}[/latex]
- [latex]{\left({r}^{3}{s}^{-2}\right)}^{4}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=14047&theme=oea&iframe_resize_id=mom25
https://ohm.lumenlearning.com/multiembedq.php?id=14058&theme=oea&iframe_resize_id=mom30
https://ohm.lumenlearning.com/multiembedq.php?id=14059&theme=oea&iframe_resize_id=mom40
In the following video we show more examples of how to find hte power of a product.
Finding the Power of a Quotient
To simplify the power of a quotient of two expressions, we can use the power of a quotient rule, which states that the power of a quotient of factors is the quotient of the powers of the factors. For example, let’s look at the following example.
Let’s rewrite the original problem differently and look at the result.
It appears from the last two steps that we can use the power of a product rule as a power of a quotient rule.
A General Note: The Power of a Quotient Rule of Exponents
For any real numbers [latex]a[/latex] and [latex]b[/latex] and any integer [latex]n[/latex], the power of a quotient rule of exponents states that
Example: Using the Power of a Quotient Rule
Simplify each of the following quotients as much as possible using the power of a quotient rule. Write answers with positive exponents.
- [latex]{\left(\dfrac{4}{{z}^{11}}\right)}^{3}[/latex]
- [latex]{\left(\dfrac{p}{{q}^{3}}\right)}^{6}[/latex]
- [latex]{\left(\dfrac{-1}{{t}^{2}}\right)}^{27}[/latex]
- [latex]{\left({j}^{3}{k}^{-2}\right)}^{4}[/latex]
- [latex]{\left({m}^{-2}{n}^{-2}\right)}^{3}[/latex]
Try It
Simplify each of the following quotients as much as possible using the power of a quotient rule. Write answers with positive exponents.
- [latex]{\left(\dfrac{{b}^{5}}{c}\right)}^{3}[/latex]
- [latex]{\left(\dfrac{5}{{u}^{8}}\right)}^{4}[/latex]
- [latex]{\left(\dfrac{-1}{{w}^{3}}\right)}^{35}[/latex]
- [latex]{\left({p}^{-4}{q}^{3}\right)}^{8}[/latex]
- [latex]{\left({c}^{-5}{d}^{-3}\right)}^{4}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=14046&theme=oea&iframe_resize_id=mom50
https://ohm.lumenlearning.com/multiembedq.php?id=14051&theme=oea&iframe_resize_id=mom60
https://ohm.lumenlearning.com/multiembedq.php?id=43231&theme=oea&iframe_resize_id=mom60
Simplifying Exponential Expressions
Recall that to simplify an expression means to rewrite it by combing terms or exponents; in other words, to write the expression more simply with fewer terms. The rules for exponents may be combined to simplify expressions.
Example: Simplifying Exponential Expressions
Simplify each expression and write the answer with positive exponents only.
- [latex]{\left(6{m}^{2}{n}^{-1}\right)}^{3}[/latex]
- [latex]{17}^{5}\cdot {17}^{-4}\cdot {17}^{-3}[/latex]
- [latex]{\left(\dfrac{{u}^{-1}v}{{v}^{-1}}\right)}^{2}[/latex]
- [latex]\left(-2{a}^{3}{b}^{-1}\right)\left(5{a}^{-2}{b}^{2}\right)[/latex]
- [latex]{\left({x}^{2}\sqrt{2}\right)}^{4}{\left({x}^{2}\sqrt{2}\right)}^{-4}[/latex]
- [latex]\dfrac{{\left(3{w}^{2}\right)}^{5}}{{\left(6{w}^{-2}\right)}^{2}}[/latex]
Try It
Simplify each expression and write the answer with positive exponents only.
- [latex]{\left(2u{v}^{-2}\right)}^{-3}[/latex]
- [latex]{x}^{8}\cdot {x}^{-12}\cdot x[/latex]
- [latex]{\left(\frac{{e}^{2}{f}^{-3}}{{f}^{-1}}\right)}^{2}[/latex]
- [latex]\left(9{r}^{-5}{s}^{3}\right)\left(3{r}^{6}{s}^{-4}\right)[/latex]
- [latex]{\left(\frac{4}{9}t{w}^{-2}\right)}^{-3}{\left(\frac{4}{9}t{w}^{-2}\right)}^{3}[/latex]
- [latex]\dfrac{{\left(2{h}^{2}k\right)}^{4}}{{\left(7{h}^{-1}{k}^{2}\right)}^{2}}[/latex]
https://ohm.lumenlearning.com/multiembedq.php?id=14056&theme=oea&iframe_resize_id=mom70
https://ohm.lumenlearning.com/multiembedq.php?id=14057&theme=oea&iframe_resize_id=mom80
https://ohm.lumenlearning.com/multiembedq.php?id=14060&theme=oea&iframe_resize_id=mom90
https://ohm.lumenlearning.com/multiembedq.php?id=43896&theme=oea&iframe_resize_id=mom95
In the following video we show more examples of how to find the power of a quotient.