In Chapters 1 and 2, we learned about powers of whole numbers, fractions, and decimal numbers.
Recall that when a number is raised to a whole number exponent, we can think of it as repeated multiplication. Powers are a simpler way to indicate repeated multiplication, similar to how multiplication is a simpler way to indicate repeated addition. Powers are expressed using exponential notation.
For example, the whole number 2 multiplied by itself 5 times is written in exponential notation as:
base [latex] \longrightarrow2^{5\longleftarrow} [/latex] exponent
2 is the base, 5 is the exponent, and the whole representation 25 is known as the power.
Similarly, the fraction [latex] \displaystyle{\frac{3}{4}} [/latex] multiplied by itself 4 times is written in exponential notation as:
base [latex] \longrightarrow\displaystyle{\left(\frac{3}{4}\right)}^{4\nwarrow} [/latex] exponent
[latex] \displaystyle{\frac{3}{4}} [/latex] is the base, 4 is the exponent, and the whole representation [latex] \displaystyle{\left(\frac{3}{4}\right)}^4 [/latex] is the power.
Similarly, the decimal number 1.2 multiplied by itself 3 times is written in exponential notation as:
base [latex] \longrightarrow(1.2)^{3\longleftarrow} [/latex] exponent
1.2 is the base, 3 is the exponent, and the whole representation [latex] (1.2)^3 [/latex] is the power.
The following properties of exponents, known as the rules or laws of exponents, are used to simplify expressions that involve exponents.
To multiply powers with the same base, add their exponents.
For example,
[latex] 7^5 \times 7^3 = (7 \times 7 \times 7 \times 7 \times 7) \times (7 \times 7 \times 7) [/latex]
[latex] = (7 \times 7 \times 7 \times 7 \times 7 \times 7 \times 7 \times 7) [/latex]
[latex] = 7^8[/latex], which is the same as [latex] = 7^{(5 + 3)}[/latex]
You will note that the resulting exponent, 8, can be obtained by adding the exponents 5 and 3 since the powers have the same base.
In general, for powers with base ‘a’ and exponents ‘m’ and ‘n’,
[latex] \boldsymbol{a^m \times a^n = a^{(m + n)}} [/latex]
Note: [latex] a^m + a^n \neq a^{(m + n)} [/latex]
Express the following as a single power:
[latex] 2^3 \times 2^4 \times 2^2 [/latex]
[latex] \displaystyle{\left(\frac{3}{5}\right)^6 \times \left(\frac{3}{5}\right)^2} [/latex]
[latex] (0.2)^3 \times (0.2)^2 [/latex]
[latex] 2^3 \times 2^4 \times 2^2 = 2^{(3 + 4 + 2)} = 2^9 [/latex]
[latex] \displaystyle{\left(\frac{3}{5}\right)^6 \times \left(\frac{3}{5}\right)^2 = \left(\frac{3}{5}\right)^{(6 + 2)} = \left(\frac{3}{5}\right)^8} [/latex]
[latex] (0.2)^3 \times (0.2)^2 = (0.2)^{3 + 2} = (0.2)^5 [/latex]
To divide two powers with the same base, subtract their exponents.
For example,
[latex] 4^7 \div 4^2 = \displaystyle{\frac{4 \times 4 \times 4 \times 4 \times 4 \times 4 \times 4}{4 \times 4}} [/latex]
[latex] = \displaystyle{\frac{4 \times 4}{4 \times 4} \times 4 \times 4 \times 4 \times 4 \times 4} [/latex]
[latex] = 1 \times 4 \times 4 \times 4 \times 4 \times 4 [/latex]
[latex] = 4^5[/latex], which is the same as [latex] = 4^{(7 - 2)} [/latex]
You will note that the resulting exponent, 5, can be obtained by subtracting the exponent of the denominator from the exponent of the numerator (7 − 2 = 5) since the powers have the same base.
In general, for powers with a non-zero base ‘a’ and exponents ‘m’ and ‘n’,
[latex] \boldsymbol{\displaystyle{\frac{a^m}{a^n} = a^{(m - n)}}}[/latex], where [latex] \boldsymbol{a \neq 0} [/latex]
Note: [latex] a^m - a^n \neq a^{(m - n)} [/latex]
Express the following as a single power:
[latex] 3^9 \div 3^5 [/latex]
[latex] \displaystyle{\left(\frac{2}{3}\right)^6 \div \left(\frac{2}{3}\right)^4} [/latex]
[latex] (1.15)^5 \div (1.15)^2 [/latex]
[latex] 3^9 \div 3^5 = 3^{(9 - 5)} = 3^4 [/latex]
[latex] \displaystyle{\left(\frac{2}{3}\right)^6 \div \left(\frac{2}{3}\right)^4 = \left(\frac{2}{3}\right)^{6 - 4} =\left(\frac{2}{3}\right)^2} [/latex]
[latex] (1.15)^5 \div (1.15)^2 = (1.15)^{(5 - 2)} = (1.15)^3 [/latex]
To determine the power of a product, each factor of the product is raised to the indicated power.
For example,
[latex] (3 \times 5)^4 = (3 \times 5)(3 \times 5)(3 \times 5)(3 \times 5) [/latex]
[latex] = 3 \times 3 \times 3 \times 3 \times 5 \times 5 \times 5 \times 5 [/latex]
[latex] = 3^4 \times 5^4 [/latex]
You will note from the result that each factor of the product is raised to the power of 4.
In general, for any product of factors ‘a’ and ‘b’ that is raised to the power ‘n’,
[latex] \boldsymbol{(a \times b)^n = a^n \times b^n} [/latex]
Express the following in expanded form using the Power of a Product Rule:
[latex] (8 \times 6)^3 [/latex]
[latex] \displaystyle{\left(\frac{3}{5} \times \frac{2}{7}\right)^3} [/latex]
[latex] (1.12 \times 0.6)^3 [/latex]
[latex] (8 \times 6)^3 = 8^3 \times 6^3 [/latex]
[latex] \displaystyle{\left(\frac{3}{5} \times \frac{2}{7}\right)^3 = \left(\frac{3}{5}\right)^3 \times \left(\frac{2}{7}\right)^3} [/latex]
[latex] (1.12 \times 0.6)^3 = (1.12)^3 \times (0.6)^3 [/latex]
The Power of a Quotient Rule is similar to the Power of a Product Rule. To determine the power of a quotient, raise the numerator to the indicated power and divide by the denominator raised to the indicated power.
For example,
[latex] \displaystyle{\left(\frac{5}{8}\right)^3 = \left(\frac{5}{8}\right) \times \left(\frac{5}{8}\right) \times \left(\frac{5}{8}\right)} [/latex]
[latex] \displaystyle{\frac{5 \times 5 \times 5}{8 \times 8 \times 8} = \frac{5^3}{8^3}} [/latex]
You will note from the result that the numerator and the denominator of the expression is raised to the power of 3.
In general, for any quotient with numerator ‘a’ and non-zero denominator ‘b’ that is raised to the power ‘n’,
[latex] \boldsymbol{\displaystyle{\left(\frac{a}{b}\right)^n = \frac{a^n}{b^n}}}[/latex], where [latex] \boldsymbol{b \neq 0} [/latex]
Express the following in expanded form using the Power of a Quotient Rule:
[latex] \displaystyle{(\frac{7}{4})^3} [/latex]
[latex] \left[\frac{\left(\displaystyle{\frac{2}{3}}\right)}{\left(\displaystyle{\frac{3}{5}}\right)}\right]^4 [/latex]
[latex] \displaystyle{\left(\frac{1.05}{0.05}\right)^3} [/latex]
[latex] \displaystyle{(\frac{7}{4})^3 = \frac{7^3}{4^3}} [/latex]
[latex] \left[\frac{\left(\displaystyle{\frac{2}{3}}\right)}{\left(\displaystyle{\frac{3}{5}}\right)}\right]^4 = \displaystyle{\left(\frac{2}{3} \div \frac{3}{5}\right)^4 = \left(\frac{2}{3}\right)^4 \div \left(\frac{3}{5}\right)^4 = \frac{2^4}{3^4} \div \frac{3^4}{5^4}} [/latex]
[latex] \displaystyle{\left(\frac{1.05}{0.05}\right)^3 = \frac{(1.05)^3}{(0.05)^3}} [/latex]
In order to determine the power of a power of a number, multiply the two exponents of the powers together to obtain the new exponent of the power.
For example,
[latex] (9^3)^2 = (9^3) \times (9^3) [/latex]
[latex] = (9 \times 9 \times 9) \times (9 \times 9 \times 9) [/latex]
[latex] = 9 \times 9 \times 9 \times 9 \times 9 \times 9 [/latex]
[latex] = 96[/latex], which is the same as [latex] 9^{(3 \times 2)} [/latex]
You will note that the resulting exponent, 6, can be obtained by multiplying the exponents 3 and 2.
In general, to raise the power of a number ‘a’ to a power ‘m’, and then raise it to a power ‘n’, [latex] \boldsymbol{(a^m)^n = a^{(m \times n)}} [/latex]
Express the following as a single power:
[latex] (5^4)^3 [/latex]
[latex] \displaystyle{\left[\left(\frac{3}{8}\right)^3\right]^2} [/latex]
[latex] [(1.04)^4]^2 [/latex]
[latex] (5^4)^3 = 5^{(4\times 3)} = 5^{12} [/latex]
[latex] \displaystyle{\left[\left(\frac{3}{8}\right)^3\right]^2 = \left(\frac{3}{8}\right)^{(3 \times 2)} = \left(\frac{3}{8}\right)^6} [/latex]
[latex] [(1.04)^4]^2 = (1.04)^{(4 \times 2)} = (1.04)^8 [/latex]
Solve the following:
[latex] (2^2)^3 \times 2^7 \div 2^9 [/latex]
[latex] 7^5 \div (7^3)^2 \times 7^2 [/latex]
[latex] (2^2)^3 \times 2^7 \div 2^9 = 2^6 \times 2^7 \div 2^9 = 2^{(6 + 7 - 9)} = 2^4 = 16 [/latex]
[latex] 7^5 \div (7^3)^2 \times 7^2 = 7^5 \div 7^6 \times 7^2 = 7^{(5 - 6 + 2)} = 7^1 = 7 [/latex]
Table 3.1-a summarizes the properties (rules) of exponents.
Property (Rule) | Rule in Exponential Form |
Example |
---|---|---|
Product Rule | [latex] a^m \times a^n = a^{(m + n)} [/latex] | [latex] 3^5 \times 3^4 = 3^{(5 + 4)} [/latex] |
Quotient Rule | [latex] \displaystyle{\frac{a^m}{a^n} = a^{(m - n)}} [/latex] | [latex] \displaystyle{\frac{3^7}{3^4} = 3^{(7 - 4)}} [/latex] |
Power of a Product Rule | [latex] (a \times b)^n = a^n \times b^n [/latex] | [latex] (3 \times 5)^2 = 3^2 \times 5^2 [/latex] |
Power of a Quotient Rule | [latex] \displaystyle{\left(\frac{a}{b}\right)^n = \frac{a^n}{b^n}} [/latex] | [latex] \displaystyle{\left(\frac{3}{5}\right)^3 = \frac{3^3}{5^3}} [/latex] |
Power of a Power Rule | [latex] (a^m)^n = a^{(m \times n)} [/latex] | [latex] (3^2)^3 = 3^{(2 \times 3)} [/latex] |
Table 3.1-b summarizes the properties of powers with exponents and bases of one and zero.
Property (Rule) | Description | Rule in Exponential Form |
Example |
---|---|---|---|
Base ‘a’ Exponent 1 | Any base ‘a’ raised to the exponent ‘1’ equals the base itself. | [latex] a^1 = a [/latex] | [latex] 8^1 = 8 [/latex] |
Base ‘a’ Exponent 0 | Any non-zero base ‘a’ raised to the exponent ‘0’ equals 1. | [latex] a^0 = 1 [/latex] | [latex] 8^0 = 1 [/latex] |
Base ‘1’ Exponent ‘n’ | A base of ‘1’ raised to any exponent ‘n’ equals 1. | [latex] 1^n = 1 [/latex] | [latex] 1^5 = 1 [/latex] |
Base ‘0’ Exponent ‘n’ | A base of ‘0’ raised to any positive exponent ‘n’ equals 0. | [latex] 0^n = 0 [/latex] | [latex] 0^5 = 0 [/latex] |
Base ‘0’ Exponent ‘0’ | A base of ‘0’ raised to the exponent ‘0’ is indeterminate. | [latex] 0^0 = indeterminate [/latex] |
For the addition and subtraction of powers, there is no special rule for powers with either the same or different bases. Evaluate each operation separately and then perform the addition or subtraction.
For example,
Addition of exponential expressions with the same base:
[latex] 2^3 + 2^4 [/latex] Evaluating [latex] 2^3 [/latex] and [latex] 2^4 [/latex] separately and then adding,
[latex] = 8 + 16 = 24 [/latex]
Addition of exponential expressions with different bases:
[latex] 2^2 + 3^3 [/latex] Evaluating [latex] 2^2 [/latex] and [latex] 3^3 [/latex] separately and then adding,
[latex] = 4 + 27 = 31 [/latex]
Subtraction of exponential expressions with the same base:
[latex] 5^3 - 5^2 [/latex] Evaluating [latex] 5^3 [/latex] and [latex] 5^2 [/latex] separately and then subtracting,
[latex] = 125 - 25 = 100 [/latex]
Subtraction of exponential expressions with different bases:
[latex] 4^3 - 2^3 [/latex] Evaluating [latex] 4^3 [/latex] and [latex] 2^3 [/latex] separately and then subtracting,
[latex] = 64 - 8 = 56 [/latex]
Evaluate the following:
[latex] 3^3 + 3^2 [/latex]
[latex] 5^2 + 3^2 [/latex]
[latex] 5^4 - 5^2 [/latex]
[latex] 6^2 - 4^2 [/latex]
[latex] 3^3 + 3^2 = 27 + 9 = 36 [/latex]
Note: [latex] \boldsymbol{a^m + a^n \neq a^{(m + n)}} [/latex]
[latex] 3^3 + 3^2 \neq 3^5 [/latex]
[latex] 5^2 + 3^2 = 25 + 9 = 34 [/latex]
Note: [latex] \boldsymbol{a^m + b^m \neq (a + b)^m} [/latex]
[latex] 5^2 + 3^2 \neq 8^2 [/latex]
[latex] 5^4 - 5^2 = 625 - 25 = 600 [/latex]
Note: [latex] \boldsymbol{a^m - a^n \neq a^{(m - n)}} [/latex]
[latex] 5^4 - 5^2 \neq 5^2 [/latex]
[latex] 6^2 - 4^2 = 36 - 16 = 20 [/latex]
Note: [latex] \boldsymbol{a^m - b^m \neq (a - b)^m} [/latex]
[latex] 6^2 - 4^2 \neq 2^2 [/latex]
There is also no special rule for the product or quotient of powers having different bases. Evaluate each operation separately and then perform the multipication or division.
For example,
Product of exponential expressions with different bases:
[latex] 2^4 \times 3^2 [/latex] Evaluating [latex] 2^4 [/latex] and [latex] 3^2 [/latex] separately and then multiplying,
[latex]= 16 \times 9 = 144 [/latex]
Quotient of exponential expressions with different bases:
[latex] \displaystyle{\frac{3^3}{2^4}} [/latex] Evaluating [latex] 3^3 [/latex] and [latex] 2^4 [/latex] separately and then dividing,
[latex]= \displaystyle{\frac{27}{16} = 1.6875} [/latex]
Evaluate the following:
[latex] 5^3 \times 4^2 [/latex]
[latex] 5^3 \div 3^2 [/latex]
[latex] 9^2 \times 5^1 [/latex]
[latex] 4^2 \times 5^0 [/latex]
[latex] 5^3 \times 4^2 = 125 \times 16 = 2,000 [/latex]
[latex] \displaystyle{5^3 \div 3^2 = 125 ÷ 9 = \frac{125}{9} = 13\frac{8}{9}} [/latex]
[latex] 9^2 \times 5^1 = 81 \times 5 = 405 [/latex]
[latex] 4^2 \times 5^0 = 16 \times 1 = 16 [/latex]
The exponent key on different calculators can be identified by symbols such as , , , etc.
In the following examples ‘’ will be used to to represent the exponent key.
Evaluate the following using a calculator:
[latex] 5^6 [/latex]
[latex] \displaystyle{\left(\frac{3}{2}\right)^3} [/latex]
[latex] (1.02)^4 [/latex]
[latex] 5^6 [/latex]
[latex] \displaystyle{\left(\frac{3}{2}\right)^3} [/latex]
[latex] (1.02)^4 [/latex]
For Problems 1 and 2, identify the values in the empty columns for Repeated Multiplication, Base, Exponent, and Power (Exponential Notation).
Table | Repeated Multiplication | Base | Exponent | Power (Exponential Notation) |
---|---|---|---|---|
a | [latex] 7 \times 7 \times 7 \times 7 [/latex] | Empty cell | Empty cell | Empty cell |
b | Empty cell | Empty cell | Empty cell | [latex] 9^5 [/latex] |
c | Empty cell | [latex] 3 [/latex] | [latex] 4 [/latex] | Empty cell |
d | [latex] \displaystyle{\frac{2}{5} \times \frac{2}{5} \times \frac{2}{5} \times \frac{2}{5} \times \frac{2}{5} \times \frac{2}{5}} [/latex] | Empty cell | Empty cell | Empty cell |
e | Empty cell | Empty cell | Empty cell | [latex] \displaystyle{\left(\frac{5}{7}\right)^5} [/latex] |
f | Empty cell | [latex] \displaystyle{\left(\frac{4}{7}\right)} [/latex] | [latex] 3 [/latex] | Empty cell |
g | [latex] (1.15) \times (1.15) \times (1.15) \times (1.15) [/latex] | Empty cell | Empty cell | Empty cell |
h | Empty cell | Empty cell | Empty cell | [latex] (1.6)^3 [/latex] |
i | Empty cell | [latex] (1.25) [/latex] | [latex] 5 [/latex] | Empty cell |
Table | Repeated Multiplication | Base | Exponent | Power (Exponential Notation) |
---|---|---|---|---|
a | [latex] 2 \times 2 \times 2 \times 2 \times 2 \times 2 \times 2 \times 2 [/latex] | Empty cell | Empty cell | Empty cell |
b | Empty cell | Empty cell | Empty cell | [latex] 6^7 [/latex] |
c | Empty cell | [latex] 5 [/latex] | [latex] 3 [/latex] | Empty cell |
d | [latex] \displaystyle{\frac{2}{7} \times \frac{2}{7} \times \frac{2}{7} \times \frac{2}{7} \times \frac{2}{7}} [/latex] | Empty cell | Empty cell | Empty cell |
e | Empty cell | Empty cell | Empty cell | [latex] \displaystyle{\left(\frac{3}{8}\right)^4} [/latex] |
f | Empty cell | [latex] \displaystyle{\left(\frac{2}{9}\right)} [/latex] | [latex] 4 [/latex] | Empty cell |
g | [latex] (2.5) \times (2.5) \times (2.5) \times (2.5) \times (2.5) [/latex] | Empty cell | Empty cell | Empty cell |
h | Empty cell | Empty cell | Empty cell | [latex] (1.1)^5 [/latex] |
i | Empty cell | [latex] (0.75) [/latex] | [latex] 4 [/latex] | Empty cell |
Express Problems 3 to 22 as a single power and then evaluate using a calculator. Round the answer to two decimal places, wherever applicable.
[latex] 4^3 \times 4^6 [/latex]
[latex] 5^5 \times 5^6 [/latex]
[latex] \displaystyle{\left(\frac{1}{2}\right)^4\left(\frac{1}{2}\right)^3} [/latex]
[latex] \displaystyle{\left(\frac{2}{3}\right)^2\left(\frac{2}{3}\right)^3} [/latex]
[latex] \displaystyle{\left(\frac{5}{2}\right)^2\left(\frac{5}{2}\right)^3} [/latex]
[latex] \displaystyle{\left(\frac{5}{3}\right)^3\left(\frac{5}{3}\right)^2} [/latex]
[latex] (3.25)^4(3.25)^2 [/latex]
[latex] (0.75)^3(0.75)^4 [/latex]
[latex] 6^8 \div 6^3 [/latex]
[latex] 3^7 \div 3^5 [/latex]
[latex] \displaystyle{\left(\frac{2}{5}\right)^3 \div \left(\frac{2}{5}\right)^1} [/latex]
[latex] \displaystyle{\left(\frac{3}{2}\right)^4 \div \left(\frac{3}{2}\right)^3} [/latex]
[latex] (1.4)^5 \div (1.4)^2 [/latex]
[latex] (3.25)^6 \div (3.25)^5 [/latex]
[latex] [(6)^2]^3 [/latex]
[latex] [(5)^3]^2 [/latex]
[latex] \displaystyle{\left[\left(\frac{2}{3}\right)^4\right]^3} [/latex]
[latex] \displaystyle{\left[\left(\frac{3}{4}\right)^4\right]^2} [/latex]
[latex] [(2.5)^2]^3 [/latex]
[latex] [(1.03)^3]^2 [/latex]
Express Problems 23 to 34 as a power of the indicated base value.
[latex] 4^5 [/latex] as a power of 2
[latex] 9^6 [/latex] as a power of 3
[latex] 9(27)^2 [/latex] as a power of 3
[latex] 8(16)^2 [/latex] as a power of 2
[latex] \displaystyle{\frac{3^9 \times 3^2}{3^5}} [/latex] as a power of 3
[latex] \displaystyle{\frac{2^9 \times 2^1}{2^5}} [/latex] as a power of 2
[latex] \displaystyle{\frac{(2^5)^4}{4^6}} [/latex] as a power of 2
[latex] \displaystyle{\frac{(2^5)^4}{16^3}} [/latex] as a power of 2
[latex] \displaystyle{\frac{10^6}{10^0}} [/latex] as a power of 10
[latex] \displaystyle{\frac{3^7}{27}} [/latex] as a power of 3
[latex] \displaystyle{\frac{8^5}{8^3}} [/latex] as a power of 2
[latex] \displaystyle{\frac{5^6}{125}} [/latex] as a power of 5
Evaluate Problems 35 to 70.
[latex] 5^2 + 5^3 [/latex]
[latex] 4^3 + 4^2 [/latex]
[latex] 5^4 - 2^4 [/latex]
[latex] 6^3 - 4^3 [/latex]
[latex] 4^4 - 4^2 [/latex]
[latex] 6^3 - 6^1 [/latex]
[latex] 7^2 + 3^2 [/latex]
[latex] 6^2 - 4^2 [/latex]
[latex] 3^5 + 5^3 [/latex]
[latex] 4^3 + 3^4 [/latex]
[latex] 2^5 - 5^2 [/latex]
[latex] 2^6 - 6^2 [/latex]
[latex] 5^4 - 4^2 [/latex]
[latex] 10^3 - 7^2 [/latex]
[latex] 4^0 + 4^4 [/latex]
[latex] 3^0 + 3^4 [/latex]
[latex] (5 \times 4)^3 [/latex]
[latex] (10 \times 2)^4 [/latex]
[latex] (1.25 \times 4)^4 [/latex]
[latex] (5 \times 0.8)^3 [/latex]
[latex] \displaystyle{\left(\frac{2}{3} + 6\right)^5} [/latex]
[latex] \displaystyle{\left(\frac{3}{5} + 1\right)^3} [/latex]
[latex] 3^4 + 3^2 + 3^0 [/latex]
[latex] 4^2 + 4^4 + 4^0 [/latex]
[latex] 2^4 + 3^4 - 1^4 [/latex]
[latex] 3^3 + 2^3 - 1^3 [/latex]
[latex] \displaystyle{\left(\frac{1}{2}\right)^3 + \left(\frac{1}{2}\right)^2 + \left(\frac{1}{2}\right)^0} [/latex]
[latex] \displaystyle{\left(\frac{1}{5}\right)^2 + \left(\frac{1}{5}\right)^0 + \left(\frac{1}{5}\right)^4} [/latex]
[latex] (2.1)^2 + (2.1)^0 [/latex]
[latex] (3.2)^2 + (3.2)^1 [/latex]
[latex] 4^3 \times 3^4 [/latex]
[latex] 7^2 \times 2^2 [/latex]
[latex] 6^4 ÷ 5^4 [/latex]
[latex] 8^2 ÷ 7^2 [/latex]
[latex] (2 \times 3^2)^4 [/latex]
[latex] (5 \times 2^2)^3 [/latex]