Exponents can be represented as positive integers, negative integers, or zero.
See Exponent Basics for more information on positive integer exponents (or zero).
Negative Integer Exponents 
The use of a negative integer exponent has special meaning and a rule explaining its use.

For any nonzero number x, and for any positive integer n,

The use of a positive exponent is an application of repeated multiplication by the base:
4^{3} = 4 • 4 • 4 = 64.
The use of a negative exponent produces the opposite of repeated multiplication.
It can be thought of as a form of repeated division by the base:
4^{3} = 1 ÷ 4 ÷ 4 ÷ 4 = 0.015625
Examples:
1. Notice: making x^{1} the reciprocal of x. 
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