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{{ printedBook.courseTrack.name }} {{ printedBook.name }} Using Properties of Exponents

The properties of exponents are a set of tools that can be used to simplify expressions with exponents.

Product of Powers Property

The product of two powers with the same non-zero base a and integer exponents m and n can be written as a single power with base a and exponent m+n.

Proof

To prove the identity, it will be shown that the left-hand side is equivalent to the right-hand side. To do so, and will be written as products using the definition of a power.
With this information, the left-hand side of the identity can be rewritten using multiplication.
By the definition of a power, multiplying a number by itself m+n times is equivalent to raising that number to the power of m+n.
The Product of Powers Property has been proved.

Quotient of Powers Property

The ratio of two powers with the same non-zero base a and integer exponents m and n can be written as a single power with base a and exponent mn.

Proof

To prove the identity, it will be shown that the left-hand side is equivalent to the right-hand side. To do so, and will be written as products using the definition of a power.
Next, the common factors will be eliminated. It will be arbitrarily assumed that m>n.
Note that when the quotient is simplified, the number of remaining factors will be mn.
Finally, the definition of a power will be used one more time to express the right-hand side of the above equation as a single power. With this last step, the Quotient of Powers Property is proven.

Note that this property is also valid for mn. If m=n, then the exponent will be zero. If m<n, the exponent will be negative.

Power of a Power Property

A power with a non-zero base a an integer exponent m that is raised to another integer exponent n can be written as a power with base a and exponent mn.

For the rule to be true for a=0, both exponents must be greater than zero.

Proof

To prove the identity, it will be shown that the left-hand side is equivalent to the right-hand side. To do so, will be rewritten as a product using the definition of a power.
Then, all occurrences of the expression will be written as products using the definition of a power one more time.
Notice that the base a is multiplied by itself mn times. By the definition of a power, the right-hand side of the above equation is equivalent to raising a to the power of mn.
The Power of a Power Property has been proved.

Power of a Product Property

A power with an integer exponent m whose base is the product of two non-zero factors a and b can be written as the product of two powers with bases a and b and the same exponent m.

For this rule to be valid when either a or b is 0, m must be greater than zero.

Proof

To prove the identity, it will be shown that the left-hand side is equivalent to the right-hand side. To do so, will be written as a product using the definition of a power.
Next, the parentheses can be removed.
Now, the Commutative Property of Multiplication can be used.
Finally, using the definition of a power again, the right-hand side of the equation can be written as the product of and

The Power of a Product Property has been proven.

Power of a Quotient Property

A power with an integer exponent m whose base is a ratio of a non-zero numerator a to a non-zero denominator b can be written as the ratio of two powers with bases a and b and the same exponent m.

For the rule to be true for a=0, m must be greater than zero.

Proof

To prove the identity, it will be shown that the left-hand side is equivalent to the right-hand side. To do so, will be rewritten as a product using the definition of a power.
Next, the fractions will be multiplied.
Finally, using the definition of a power one more time, the right-hand side of the equation can be written as a ratio of the numerator to the denominator

The Power of a Quotient Property has been proven.

Negative Exponent

If a is a non-zero real number and n is a positive integer, then a raised to the power of -n is equal to 1 over a raised to the power of n.

It is important to note that the sign of the exponent changes, meaning that the resulting fraction is not simply the reciprocal of the original power.

Proof

To prove this identity, the Zero Exponent Property will be considered.
In the above equation, 0 will be rewritten as nn and, after some algebraic manipulation and using the Product of Powers Property, the desired result will be obtained.

Zero Exponent Property

Any non-zero real number raised to the power of 0 is equal to 1.

a0=1

Proof

To prove this identity, it will be shown that the left-hand side is always equal to 1 for any real number a. To do so, the exponent 0 will be written as a difference, for instance bb. Then, the expression will be rearranged using the Quotient of Powers Property.
a0

Rewrite 0 as bb

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Exercise
Simplify the following expression using properties of exponents.
Show Solution
Solution
To simplify the exponents in an expression, it can be helpful to focus on either one power at a time or powers with the same base. Here, we will begin with a0. The Zero Exponent Property tells us that any base with an exponent of 0 equals 1. Next, we can focus on the powers with base b. Notice that there is one in the numerator and one in the denominator. We can use the Quotient of Powers Property to simplify these.
Lastly, we can rewrite the negative exponents using the Negative Exponent Property.
We have now completely simplified the expression.

Variable Exponents

The properties of exponents are not only valid for numerical exponents. They can be applied in the same way when exponents contain variables.
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Exercise
Simplify the following expression using the properties of exponents.
Show Solution
Solution
To begin, we notice that each power in this expression has the same base. We will first focus on simplifying the numerator by applying the Product of Powers Property.
We can now simplify the fraction using the Quotient of Powers Property.
The given expression simplifies completely to