1.1.4: Integer Exponents
- Page ID
- 139009
By the end of this section, you will be able to:
- Understand the meaning of an integer exponent.
- Simplify numerical expressions with which involve integer exponents.
Before we get started, take this readiness quiz.
1. Evaluate \(-5\cdot 2\).
2. Evaluate \(-5+3\).
3. Evaluate \(3\cdot 3\cdot 3\cdot 3\).
We will begin with positive integer exponents where the meaning is straight forward. The positive integer exponent indicates repeated multiplication of the same quantity. For example, in the expression \(a^m\), the positive integer exponent \(m\) tells us how many times we use the base \(a\) as a factor.
\(a^m=\underbrace{a\cdot a\cdot \cdots\cdot a}_{m a'\text{s}}\)
For example,
\((−9)^5=(−9)(−9)(−9)(−9)(−9)\).
Let’s review the vocabulary for expressions with exponents.
\(a^m=\underbrace{a\cdot a\cdots a}_{m a'\text{s}}\)
This is read \(a\) to the \(m\)th (power), or \(a\) to the power \(m\).
In the expression \(a^m\) with positive integer \(m\) and \(a\not=0\), the exponent \(m\) tells us how many times we use the base \(a\) as a factor.
a. Evaluate \(2^3\).
b. Evaluate \(−7^2\).
c. Evaluate \((−1)^4\).
d. Write using exponents: \(−2\cdot 2\cdot 2\).
e. Identify the base and the exponent: \(-4^3\).
Solution
a. \(2^3=2\cdot 2\cdot 2=8\)
b. \(−7^2=-49\)
c. \((-1)^4=(-1)\cdot(-1)\cdot(-1)\cdot(-1)=1\)
d. \(-2\cdot 2\cdot 2=-2^3\)
e. \(-4^3\) has an exponent of 3 and the base is 4 since there are no parentheses that indicate including the "-".
a. Evaluate \(3^4\).
b. Evaluate \(−2^4\).
c. Evaluate \((-2)^3\).
d. Write using exponents \(-6\cdot 6\cdot 6\cdot 6\).
e. Identify the base and the exponent: \(-2\cdot 5^7\).
- Answer
-
a. 81
b. -16
c. -8
d. \(-6^4\)
e. The exponent is 7 and the base is 5 (since there are no parentheses that would include 2 or -2).
We will now investigate several properties of exponents. First we will look at an example that leads to the Product Property for Positive Integer Exponents.
|
\(\quad 7^{2} 7^{3}\) |
|
|---|---|
| What does this mean? |
\(=\underbrace{7 \cdot 7}_{2 \text{ factors}\space} \cdot \underbrace{ 7\cdot 7\cdot 7}_{3 \text{ factors}}\) \(=\underbrace{7\cdot 7\cdot 7\cdot 7\cdot 7}_{5 \text{ factors}}\) |
| \(= 7^{5}\) |
The base stayed the same and we added the exponents. Remember that the exponent counts the number of bases we multiply so, we are multiplying \(2\) sevens by \(3\) sevens which gives us a total of \(5\) sevens!
In general we have:
If \(a\) is a real number and \(m\) and \(n\) are positive integers, then
\[a^ma^n=a^{m+n}. \nonumber\]
To multiply with like bases, add the exponents.
Simplify each expression:
a. \(3^53^6\)
b. \(2^4\cdot 2^{3\cdot 4}\)
c. \(2\cdot 5^7\cdot 3 \cdot 5\)
d. \(11^4 11^5 11^2\)
Solution
a.
| \(\quad 3^5 3^6\) | |
|---|---|
| Use the Product Property, \(a^ma^n=a^{m+n}\) or directly use the fact that the exponent counts. | \(=3^{5+6}\) |
| Simplify. | \(=3^{11}\) |
b.
| \(\quad\; 2^4\cdot 2^{3\cdot 4}\) | |
|---|---|
| Use the Product Property, \(a^ma^n=a^{m+n}\) or or directly use the fact that the exponent counts.. | \(=2^{4+3\cdot 4}\) |
| Simplify. |
\(=2^{4\cdot 4}\) \(=2^{16}\) |
c.
| \(\quad\; 2\cdot 5^7\cdot 3\cdot 5\) | |
|---|---|
| Rewrite, \(a=a^1\). | \(= 2\cdot 5^7\cdot 3\cdot 5^1\) |
| Use the Commutative Property and use the Product Property, \(a^ma^n=a^{m+n}\) or or directly use the fact that the exponent counts.. |
\(=2\cdot 3\cdot 5^{7+1}\) |
| Simplify. | \(=6\cdot 5^8\) |
d.
| \(\quad 11^4 11^5 11^2\) | |
|---|---|
| Add the exponents, since the bases are the same. | \(= 11^{4+5+2}\) |
| Simplify. | \(=11^{11}\) |
Simplify each expression:
a. \(7^9 7^8\)
b. \(4^{2\cdot 3}\cdot 4^3\)
c. \(3\cdot 9^5\cdot 4\cdot 9\)
d. \(3^6 3^4 3^8\)
- Answer
-
a. \(7^{17}\)
b. \(4^9\)
c. \(12\cdot 9^6\)
d. \(3^{18}\)
Simplify each expression:
a. \((-2)^{12}(-2)^4\)
b. \(10\cdot 10^5\)
c. \(2\cdot 4\cdot 6\cdot 4^7\)
d. \(6^5 6^9 6^5\)
- Answer
-
a. \((-2)^{16}=2^{16}\)
b. \(10^{6}\)
c. \(12\cdot 4^8\)
d. \(6^{19}\)
Now let’s look at an exponential expression that contains a power raised to a power. Let's see if we can discover a general property.
| \(\quad (5^2)^3\) | |
|---|---|
| What does this mean? | \(=5^25^25^2\) |
| How many factors altogether? |
\(=\underbrace{5\cdot 5}_{2\; factors }\cdot \underbrace{5\cdot 5}_{2\text{ factors }}\cdot \underbrace{5\cdot 5}_{2\text{ factors }}\) \(=\underbrace{5\cdot 5\cdot 5\cdot 5 \cdot 5\cdot 5}_{6\text{ factors }}\) |
| So we have | \(=5^6\) |
Notice the 6 is the product of the exponents, 2 and 3. We see that \((5^2)^3\) is \(5^{2\cdot 3}\) or \(x^6\). We can also see that
In this example we multiplied the exponents.
We can check various examples to see that this leads us to the Power Property for Positive Integer Exponents.
If \(a\) is a real number and \(m\) and \(n\) are positive integers, then
\[(a^m)^n=a^{mn}. \nonumber \]
To raise a power to a power, multiply the exponents.
Simplify each expression:
a. \((3^5)^9\)
b. \((4^{4})^7\)
c. \((2^3)^6(2^5)^4\)
Solution
a.
| \((3^5)^9\) | |
|---|---|
| Use the power property, \((a^m)^n=a^{mn}\) or use the fact that the exponent counts the number of bases being multiplied. | \(3^{5\cdot 9}\) |
| Simplify. | \(3^{45}\) |
b.
| \(\quad(4^{4})^7\) | |
|---|---|
| Use the power property. | \(=4^{4\cdot 7}\) |
| Simplify. | \(=4^{28}\) |
c.
| \(\quad (2^3)^6(2^5)^4\) | |
|---|---|
| Use the power property. | \(=2^{18}2^{20}\) |
| Add the exponents. | \(=2^{38}\) |
Simplify each expression:
a. \(((-3)^7)^5\)
b. \((5^4)^{3}\)
c. \((3^4)^5(3^7)^4\)
- Answer
-
a. \((-3)^{35}=-3^{35}\)
b. \(5^{12}\)
c. \(3^{48}\)
Simplify each expression:
a. \((9^6)^9\)
b. \((3^{7})^7\)
c. \(\left(\left(\frac12\right)^4\right)^5\left(\left(\dfrac12\right)^3\right)^3\)
- Answer
-
a. \(9^{54}\)
b. \(3^{49}\)
c. \(\left(\dfrac12\right)^{29}\)
We will now look at an expression containing a product that is raised to a power. Can we find this pattern?
| \(\quad(2\cdot 5)^3\) | |
|---|---|
| What does this mean? | \(=2\cdot 5\cdot 2\cdot 5 \cdot 2\cdot 5\) |
| We group the like factors together. | \(=2\cdot 2\cdot 2\cdot 5\cdot 5\cdot 5\) |
| How many factors of \(2\) and of \(5\)? | \(=2^3 5^3\) |
Notice that each factor was raised to the power and \((2\cdot 5)^3\) is \(2^3 5^3\).
The exponent applies to each of the factors! We can say that the exponent distributes over multiplication. If we were to check various examples with exponents we would find the same pattern emerges. This leads to the Product to a Power Property for Postive Integer Exponents.
If \(a\) and \(b\) are real numbers and \(m\) is a positive integer, then
\[(ab)^m=a^mb^m \nonumber. \]
To raise a product to a power, raise each factor to that power.
Simplify each expression using the Product to a Power Property:
a. \((−3 \cdot 2)^3\)
b. \((6\cdot 4^3)^{2}\)
c. \((5\cdot 4^{3})^2\)
Solution
a.
| \(\quad(−3 \cdot 2)^3\) | |
|---|---|
| Use Power of a Product Property, \((ab)^m=a^mb^m\). | \(=(−3)^3 2^3\) |
| Simplify. | \(=−27 \cdot 8=-216\) |
b.
| \(\quad (6 \cdot 4^3)^{2}\) | |
|---|---|
| Use the Power of a Product Property, \((ab)^m=a^mb^m\). | \(=6^{2}(4^3)^{2}\) |
| Use the Power Property, \((a^m)^n=a^{mn}\). | \(=6^{2}4^{6}\) |
| Simplify. | \(=36\cdot 4^6\) |
c.
| \(\quad(5\cdot 4^{3})^2\) | |
|---|---|
| Use the power of a product property, \((ab)^m=a^mb^m\). | \(=5^2(4^{3})^2\) |
| Simplify. | \(=25\cdot 4^{6}\) |
Simplify each expression using the Product to a Power Property:
a. \((2\cdot 3)^5\)
b. \((2\cdot (-2)^3)^{4}\)
c. \((8(-2)^{4})^2\)
- Answer
-
a. \(32\cdot 3^5\)
b. \(16(-2)^{12}=16\cdot 2^{12}=2^{16}\)
c. \(64 (-2)^8=64\cdot 2^8=2^{14}\)
Simplify each expression using the Product to a Power Property:
a. \((−3\cdot 2)^3\)
b. \((−4\cdot 10^4)^{2}\)
c. \((2\cdot 10^{4})^3\)
- Answer
-
a. \(−27\cdot 2^3=-27\cdot 8=-216\)
b. \(16\cdot 10^8\)
c. \(8\cdot 10^{12}\)
Because division is multiplication by a recipricol, the exponent must distribute over division as well as multiplication. We give a specific example here:
\[\left(\dfrac{4}{3}\right)^3= \dfrac{4}{3}\cdot \dfrac{4}{3}\cdot \dfrac{4}{3}=\dfrac{4^3}{3^3}\nonumber.\]
So we have also the quotient property.
If \(a\) and \(b(\not=0\) are real numbers and \(m\) is a positive integer, then
\[\left(\dfrac{a}{b}\right)^m=\dfrac{a^m}{b^m} \nonumber. \]
To raise a product to a power, raise each factor to that power.
Rewrite \(\left(\dfrac{3}{5}\right)^3\) using the Quotient to a Power property
Solution
\(\left(\dfrac{3}{5}\right)^3=\dfrac{4^3}{5^3}\).
Rewrite \(\left(\dfrac{1}{2}\right)^5\) using the Quotient to a Power property
- Answer
-
\(\frac{1}{2^5}\).
Rewrite \(\left(\dfrac{-2}{3}\right)^4\) using the Quotient to a Power property
- Answer
-
\(\dfrac{(-2)^4}{3^4}\). This is equal to \(\dfrac{16}{81}\) but this isn't what is asked here.
Now we will extend the meaning to all integers.
Extending the Meaning of Exponent to Integers
Note that, while so far an exponent that is not a positive integer has no meaning, we see that blindly applying the above properties for such exponents leads to a couple definitions.
To give an idea of the argument we begin with a specific example. So far we do not have a meaning for \(7^0\) nor for \(7^{-3}\) since the exponents in these examples are not counting numbers. We will assume the rules of exponents apply because we would like the meaning of integer exponents to be consistent with these rules.
We know
| \(7^0 7^1\) | |
|---|---|
|
Using the addition of exponents. |
\(=7^{0+1}\) |
|
Simplify the exponent. |
\(=7^1\) |
| Conclude. |
\(7^0 7=7\) |
| \(7^0\) is the number that when you multiply it by \(7\) the result is \(7\). | \(7^0=1.\) |
|---|
We could replace \(7\) with any non-zero number and have the same conclusion! So any non-zero number to the zeroth power is 1.
So, in general, if the Product Property is also to hold for the exponent zero we must define, for \(a\not= 0\),
\[a^0=1. \nonumber \]
Now, so far, \(7^{-3}\) has no meaning. But if it did, and that meaning is consistent with the properties of exponents, then, for example
| \(\quad 7^{-3}7^3\) | |
|---|---|
| Blindly applying the product property. | \(=7^{-3+3}\) |
| Simplify exponent. | \(=7^0\) |
| Using our new definition: \(x^0=1\). | \(=1\) |
| Draw conclusion. | \(7^{-3}7^3=1\) |
| Note the property of the reciprocal. | \(7^{-3}\) is the reciprocal of \(7^3\). |
| Rewrite in symbols. | \(7^{-3}=\dfrac{1}{7^3}\) |
In the argument above, we can replace \(7\) with any non-zero number and \(3\) with any positive counting number and \(-3\) with its opposite and arrive at a similar conclustion. So a negative exponent indicates a recipricol of the expression where the exponent is positive.
So, we must define
For \(a\) any non-zero real number
\[a^0=1\nonumber\]
and for \(m\) any positive integer
\[a^{-m}=\dfrac{1}{a^m} \text{ or, equivalently, }\dfrac{1}{a^{-m}}=a^m.\nonumber\]
Simplify each expression:
a. \(9^0\)
b. \((-2)^0\)
c. \((−4\cdot 5^2)^0\)
d. \(-3^0\)
Solution
The definition says any non-zero number raised to the zero power is \(1\).
a. Use the definition of the zero exponent. \(9^0 = 1\)
b. Use the definition of the zero exponent. \((-2)^0 = 1\)
c. Anything raised to the power zero is 1. Here the base is \(-4\cdot 5^2 \), so \((−4\cdot 5^2)^0=1\)
d. Anything raised to the power zero is 1. Here the base is 3, so this is the opposite of \(3^0\), or, the opposite of 1. So, \(-3^0=-1\)
Simplify each expression:
a. \(11^0\)
b. \((-620)^0\)
c. \((−12\cdot 5^3 8^2)^0\)
d. \(-7^0\)
- Answer
-
a. 1
b. 1
c. 1
d. -1
Simplify each expression:
a. \(23^0\)
b. \(\pi^0\)
c. \(\left(2 \left(\dfrac{-2}{7}\right)^5\right)^0\)
d. \(-17^0\)
- Answer
-
a. 1
b. 1
c. 1
d. -1
Simplify each expression. Write your answer using positive exponents.
a. \(2^{−5}\)
b. \(10^{−3}\)
c. \(\dfrac{1}{3^{−4}}\)
d. \(\dfrac{1}{3^{−2}}\)
Solution
a.
| \(\quad 2^{−5}\) | |
|---|---|
| Use the definition of a negative exponent, \(a^{−n}=\dfrac{1}{a^n}\). |
\(=\dfrac{1}{2^5}\) \(=\dfrac{1}{32}\) |
b.
| \(\quad 10^{−3}\) | |
|---|---|
| Use the definition of a negative exponent, \(a^{−n}=\dfrac{1}{a^n}\). | \(=\dfrac{1}{10^3}\) |
| Simplify. | \(=\dfrac{1}{1000}\) |
c.
| \(\quad \dfrac{1}{3^{-4}}\) | |
|---|---|
| Use the definition of a negative exponent, \(\dfrac{1}{a^{−n}}=a^n\). |
\(=3^4\) \(=81\) |
d.
| \(\quad \dfrac{1}{3^{-2}}\) | |
|---|---|
| Use the definition of a negative exponent, \(\dfrac{1}{a^{−n}}=a^n\). | \(=3^2\) |
| Simplify. | \(=9\) |
Simplify each expression. Write your answer using positive exponents.
a. \(2^{−3}\)
b. \(10^{−7}\)
c. \(\dfrac{1}{7^{−8}}\)
d. \(\dfrac{1}{4^{−3}}\)
- Answer
-
a. \(\dfrac{1}{2^3}=\dfrac18\)
b. \(\dfrac{1}{10,000,000}\)
c. \(7^8\)
d. \(64\)
Simplify each expression. Write your answer using positive exponents.
a. \(3^{−2}\)
b. \(10^{−4}\)
c. \(\dfrac{1}{(-2)2^{−7}}\)
d. \(\dfrac{1}{2^{−4}}\)
- Answer
-
a. \(\dfrac{1}{9}\)
b. \(\dfrac{1}{10,000}\)
c. \((-2)^7=-128\)
d. \(16\)
Properties of Negative Exponents
The negative exponent tells us we can rewrite the expression by taking the reciprocal of the base and then changing the sign of the exponent.
Any expression that has negative exponents is not considered to be in simplest form. We will use the definition of a negative exponent and other properties of exponents to write the expression with only positive exponents.
For example, if after simplifying an expression we end up with the expression \(x^{−3}\), we will take one more step and write \(\dfrac{1}{x^3}\). The answer is considered to be in simplest form when it has only positive exponents.
Suppose now we have a fraction raised to a negative exponent. Let’s use our definition of negative exponents to lead us to a new property.
| \(\quad\left( \dfrac{3}{4} \right)^{-2}\) | |
|---|---|
| Use the definition of a negative exponent, \(a^{−n}=\dfrac{1}{a^n}\). | \(=\dfrac{1}{\left( \dfrac{3}{4} \right)^{2}}\) |
| Simplify the denominator. | \(=\dfrac{1}{\dfrac{9}{16}}\) |
| Simplify the complex fraction. | \(=\dfrac{16}{9}\) |
| But we know that | \(\dfrac{16}{9}=\left( \dfrac{4}{3} \right)^{2}\) |
| This tells us that | \(\left( \dfrac{3}{4} \right)^{-2} = \left( \dfrac{4}{3} \right)^{2}\) |
To get from the original fraction raised to a negative exponent to the final result, we took the reciprocal of the base—the fraction—and changed the sign of the exponent.
This leads us to the Quotient to a Negative Integer Exponent Property.
If \(a\) and \(b\) are real numbers, \(a\neq 0\), \(b\neq 0\), and \(n\) is an integer, then
\[\left(\dfrac{a}{b}\right)^{−n}=\left(\dfrac{b}{a}\right)^n. \nonumber \]
Simplify each expression. Write your answer using positive exponents.
\(\left( \dfrac{5}{7} \right)^{−2}\)
Solution
| \(\quad \left( \dfrac{5}{7} \right)^{−2}\) | |
|---|---|
| Use the Quotient to a Negative Integer Exponent Property, \(\left(\dfrac{a}{b} \right)^{−n}= \left( \dfrac{b}{a} \right)^n\). | |
| Take the reciprocal of the fraction and change the sign of the exponent. | \(=\left( \dfrac{7}{5}\right)^2\) |
| Simplify. | \(=\dfrac{49}{25}\) |
Simplify each expression. Write your answer using positive exponents.
\(\left(\dfrac{2}{3}\right)^{−4}\)
Answer
-
\(\dfrac{81}{16}\)
Simplify each expression. Write your answer using positive exponents.
\(\left(\dfrac{3}{5}\right)^{−3}\)
- Answer
-
\(\dfrac{125}{27}\)
We would like to verify that the properties of positive integer exponents can be extended to all integer exponents we will postpone this until a later section when we review these properties again in the chapter on polynomials where we will use of variables freely. Though we will postpone the demonstration, it turns out that all properties of exponents that are valid for all counting numbers are also valid for integers. And they are also valid for rational numbers, if such exponents are defined appropriately (we have no meaning at this time for rational exponents in general). We will treat this under the topic of radical expressions.
We provide for reference a table of properties of exponents.
| Definition | Description |
|---|---|
| Definition of Zero Exponent | \(a^0=1,a \neq 0\) |
| Definition of Negative Exponents | \(a^{−n}=\dfrac{1}{a^n}\), or equivalently, \(\dfrac{1}{a^{−n}}=a^n\) |
| Property | Description |
|---|---|
| Product Property | \(a^m·a^n=a^{m+n}\) |
| Power Property | \((a^m)^n=a^{m·n}\) |
| Product to a Power | \((ab)^n=a^nb^n\) |
| Quotient Property | \(\dfrac{a^m}{a^n}=a^{m−n},a\neq 0\) |
| Quotient to a Power Property | \(\left(\dfrac{a}{b}\right)^m=\dfrac{a^m}{b^m},b \neq 0 \) |
| Quotient to a Negative Exponent | \(\left(\dfrac{a}{b}\right)^{−n}=\left(\dfrac{b}{a}\right)^n\) |
Simplify each expression by applying appropriate properties:
a. \((2.5 \times 10^8)\cdot(2\times 10^4)\)
b. \(\left(\dfrac{2}{5}\right)^{-2}+7^0-\left(\dfrac{2}{3}\right)^2\)
c. \(\left(\dfrac{2\cdot5 (-3)^2}{5^3(-3)^{−2}}\right)^2 \left(\dfrac{12\cdot 5 (-3)^3}{5^3(-3)^{−1}}\right)^{−1}\)
Solution
a.
| \((2.5 \times 10^8)\cdot(2\times 10^4)\) | |
|---|---|
| Rearrange product \((2.5 \cdot 2) cdot 10^8\cdot 10^4\) | \((2.5 \cdot 2) \cdot 10^8\cdot 10^4\) |
| Simplify. | \(=5\cdot 10^8 10^4\) |
| Use product property of exponents. | \(=5\cdot 10^{12}\) |
| Rewrite in original format. | \(=5\times 10^{12}\) |
b.
| \(\left(\dfrac{2}{5}\right)^{-2}+7^0-\left(\dfrac{2}{3}\right)^2\) | |
|---|---|
| Use the quotient to a negative exponent property and the definition of exponent 0. | \(\left(\dfrac{5}{2}\right)^{2}+1-\left(\dfrac{2}{3}\right)^2\) |
| Use the meaning of the positive integer exponent. | \(=\dfrac52\dfrac52+1-\dfrac23\dfrac23\) |
| Multiply fractions. | \(=\dfrac{25}{4}+1-\dfrac49\) |
| Add/Subtract fractions (find common denominator) and reduce if possible. | \(=\dfrac{225+36-16}{36}=\dfrac{245}{36}\) |
c.
|
\(\left(\dfrac{2\cdot5 (-3)^2}{5^3(-3)^{−2}}\right)^2 \left(\dfrac{12\cdot 5 (-3)^3}{5^3(-3)^{−1}}\right)^{−1}\) |
|
|---|---|
| Simplify inside the parentheses first: use the meaning of a negative exponent and the product property. |
\(=\left(\dfrac{2(-3)^2(-3)^2 }{5^2}\right)^2\left(\dfrac{12(-3)^3(-3)^1}{5^2}\right)^{−1}\) \(=\left(\dfrac{2(-3)^4}{5^2}\right)^2\left(\dfrac{12(-3)^4}{5^2}\right)^{−1}\) |
| Use the quotient to a negative exponent property | \(=\left(\dfrac{2(-3)^4}{5^2}\right)^2\left(\dfrac{5^2}{12(-3)^4}\right)^{1}\) |
| Use meaning of the exponent or the quotient property and the Product to a Power Property, \((ab)^m=a^mb^m\). |
\(=\left(\dfrac{(2(-3)^4)^2}{(5^2)^2}\right)\cdot \left(\dfrac{5^2}{12(-3)^4}\right)\) \(=\left(\dfrac{(2^2((-3)^4)^2}{(5^2)^2}\right)\cdot \left(\dfrac{5^2}{12(-3)^4}\right)\) |
| Use the power property. | \(=\left(\dfrac{(4(-3)^8}{(5^4}\right)\cdot \left(\dfrac{5^2}{12(-3)^4}\right)\) |
| Multiply fractions. | \(=\left(\dfrac{(4(-3)^8 5^2}{12(-3)^45^4}\right)\) |
| Simplify. |
\(=\dfrac{(-3)^4}{3 5^2}\) \(=\dfrac{3^3}{5^2}\) \(=\dfrac{27}{25}\) |
Simplify each expression by applying appropriate properties:
a. \((9 \times 10^7)\div (3\times 10^{-4})\)
b. \(\left(\dfrac{3}{2}\right)^{-3}-2^0-\left(\dfrac{1}{2}\right)^{-2}\)
c. \(\left(\dfrac{3(-2)5^2}{(-2)^2(5)^{−3}}\right)^2\)
- Answer
-
a. \(3\times 10^11\)
b. \(\dfrac{-227}{27}\)
c. \(\dfrac{95^{10}}{2^2}=\dfrac{9\cdot 5^10}{4}\) To find the actual value you might want to use a calculator.
Simplify each expression by applying appropriate properties:
a. \(\dfrac{8 \times 10^{-3}}{2\times 10^{-7}}\)
b. \(\left(\dfrac{2}{3}\right)^{-1}+2^{-2}-\left(\dfrac{2}{3}\right)^0\)
c. \(\left(\dfrac{4\cdot 2^33^2}{2^23^{−1}}\right)^2\left(\dfrac{8\cdot 2 3^{−3}}{2^2\cdot 3}\right)^{−1}\)
- Answer
-
a. \(4\times 10^4\)
b. \(\dfrac34\)
c. \(2\cdot 2^33^{10}=16\cdot 3^10\). To find the value you might want to use a calculator.
- How is the negative exponent related to reciprocals? Give an example.
- How are positive and negative exponents used in science to express large or small numbers?
- What is the purpose in writing numbers this way?
a. Simplify \(\left(\dfrac{3\cdot 5^{−3}}{(-2)^{−5}}\right)^{−3}\). Write your final answer with positive exponents only.
b. Simplify \(\dfrac{36(-3)^5 2^{10}}{70(-3)^{15}2^5}\). Write your final answer with positive exponents only.
Key Concepts
- Exponential Notation
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This is read \(a\) to the \(m^{\mathrm{th}}\) power.
In the expression \(a^m\), the exponent \(m\) (when positive) tells us how many times we use the base \(a\) as a factor. - Zero Exponent (Definition) If \(a\) is a non-zero number, then \(a^0=1\).
- Negative Exponent (Definition) If \(n\) is an integer and \(a\neq 0\), then \(a^{−n}=\dfrac{1}{a^n}\) or, equivalently, \(\dfrac{1}{a^{−n}}=a^n\).
- Product Property for Exponents
If \(a\) is a real number and \(m\) and \(n\) are integers, then\[a^ma^n=a^{m+n} \nonumber \]
To multiply with like bases, add the exponents. - Quotient Property for Exponents
If \(a\) is a real number, \(a\neq 0\), and \(m\) and \(n\) are integers, then\[\begin{array} {lllll} {\dfrac{a^m}{a^n}=a^{m−n},} &{m>n} &{\text{and}} &{\dfrac{a^m}{a^n}=\dfrac{1}{a^{n−m}},} &{n>m}\\ \nonumber \end{array}\]
- Quotient to a Negative Exponent Property
If \(a\) and \(b\) are real numbers, \(a\neq 0\), \(b\neq 0\) and \(n\) is an integer, then\[\left(\dfrac{a}{b}\right)^{−n}=\left(\dfrac{b}{a}\right)^n\nonumber \]
- Power Property for Exponents
If \(a\) is a real number and \(m\) and \(n\) are integers, then\[(a^m)^n=a^{mn}\nonumber \]
To raise a power to a power, multiply the exponents. - Product to a Power Property for Exponents
If \(a\) and \(b\) are real numbers and \(m\) is a whole number, then\[(ab)^m=a^mb^m \nonumber \]
To raise a product to a power, raise each factor to that power. - Quotient to a Power Property for Exponents
If \(a\) and \(b\) are real numbers, \(b\neq 0\), and \(m\) is an integer, then\[\left(\dfrac{a}{b}\right)^m=\dfrac{a^m}{b^m} \nonumber \]
To raise a fraction to a power, raise the numerator and denominator to that power. - Summary of Exponent Properties
If \(a\) and \(b\) are real numbers, and \(m\) and \(n\) are integers, then -
Property Description Definition of Zero Exponent \(a^0=1,a \neq 0\) Definition of Negative Exponents \(a^{−n}=\dfrac{1}{a^n}\), or equivalently, \(\dfrac{1}{a^{−n}}=a^n\) -
Property Description Product Property \(a^m·a^n=a^{m+n}\) Power Property \((a^m)^n=a^{m·n}\) Product to a Power \((ab)^n=a^nb^n\) Quotient Property \(\dfrac{a^m}{a^n}=a^{m−n},a\neq 0\) Quotient to a Power Property \(\left(\dfrac{a}{b}\right)^m=\dfrac{a^m}{b^m},b \neq 0 \) Quotient to a Negative Exponent \(\left(\dfrac{a}{b}\right)^{−n}=\left(\dfrac{b}{a}\right)^n\)