Powers of Negative Numbers
Since an exponent on a number indicates multiplication by that same number,
an exponent on a negative number is
simply the negative number multiplied by itself a certain number of
times:
(- 4)3 = - 4× -4× - 4 = - 64
(- 4)3 = - 64 is negative because there are 3 negative signs--see
Multiplying
Negatives.
(- 5)2 = - 5× - 5 = 25
(- 5)2 = 25 is positive because there are 2 negative signs.
Since an odd number of negative numbers multiplied together is always a negative
number and an even number of negative numbers multiplied together is always a
positive number, a negative number with an odd exponent will always be negative
and a negative number with an even exponent will always be positive. So, to
take a power of a negative number, take the power of the (positive) opposite of
the number, and add a negative sign if the exponent is odd.
Example 1: (- 3)4 = ?
1. Take the power of the positive opposite. 34 = 81.
2. The exponent (4) is even, so (- 3)4 = 81.
Example 2: (- 7)3 = ?
1. Take the power of the positive opposite. 73 = 343
2. The exponent (3) is odd, so (- 7)3 = - 343.
Powers of Decimals
When we square 0.46, we must remember that we are multiplying
0.46×0.46, not 0.46×46.
In other words, the result has 4 decimal places, not 2.
0.462 = 0.46×0.46 = 0.2116.
When taking the power of a decimal, first count the number of decimal places in
the base number, as when multiplying decimals (see Decimal
Multiplication. Next, multiply that number
by the exponent. This will be the total number of decimal places in the answer.
Then, take the power of the base number with the decimal point removed.
Finally, insert the decimal point at the correct place, calculated in the second
step.
Example 1: 1.54 = ?
1. There is 1 decimal place and the exponent is 4. 1×4 = 4.
2. 154 = 50, 625.
3. Insert the decimal point 4 places to the right. 1.54 = 5.0625.
Example 2: 0.043 = ?
1. There are 2 decimal places and the exponent is 3. 2×3 = 6.
2. 43 = 64 = 000064.
3. Insert the decimal point 6 places to the right. 0.043 = 0.000064.
As we can see, decimals less than 1 with large exponents are generally very
small.
