We know how to find But what about ?
To work out all we need to do is find the reciprocal of the base and then raise that reciprocal to the same power but with the opposite sign .
A similar approach can be used for other powers. Let's see another example.
Evaluate
We find the reciprocal of the base and then raise that reciprocal to the same power but with the opposite sign as follows:
$3^{-2}=$
a
|
$-\dfrac {1} {9}$ |
b
|
$-9$ |
c
|
$-6$ |
d
|
$\dfrac {1} {9}$ |
e
|
$9$ |
$(-3)^{-3}=$
a
|
$-\dfrac{1}{27}$ |
b
|
$\dfrac{1}{9}$ |
c
|
$-9$ |
d
|
$-\dfrac{1}{9}$ |
e
|
$27$ |
$2^{-4} =$
a
|
$ \dfrac 1 {16}$ |
b
|
$\dfrac 1 {8}$ |
c
|
$-\dfrac 1 {16}$ |
d
|
$- \dfrac 1 {32}$ |
e
|
$-\dfrac 1 {8}$ |
Calculate the value of
We find the reciprocal of the base and then raise that reciprocal to the same power but with the opposite sign as follows:
$\left(\dfrac{1}{9}\right)^{-2}=$
a
|
$-\dfrac{1}{81}$ |
b
|
$-\dfrac{1}{18}$ |
c
|
$-\dfrac{17}{9}$ |
d
|
$18$ |
e
|
$81$ |
$\left(\dfrac 1 2\right)^{-3}=$
a
|
$8$ |
b
|
$-8$ |
c
|
$\dfrac 1 6$ |
d
|
$-\dfrac 1 8$ |
e
|
$\dfrac 1 8$ |
$\left(\dfrac 1 2\right)^{-4}=$
a
|
$16$ |
b
|
$32$ |
c
|
$\dfrac{1}{16}$ |
d
|
$8$ |
e
|
$\dfrac{1}{8}$ |
Express as a base raised to a negative exponent.
First, we write as a base raised to a power:
Now, we find the reciprocal of the base and then raise that reciprocal to the same power but with the opposite sign as follows:
Express $\dfrac {1} {25} $ as a base raised to a negative exponent.
a
|
$2^{-5}$ |
b
|
$-5$ |
c
|
$-\dfrac{1}{25}$ |
d
|
$ -5^{2}$ |
e
|
$ 5^{-2}$ |
Express $\dfrac {9} {4} $ as a base raised to a negative exponent.
a
|
$-\left(\dfrac23\right)^{2}$ |
b
|
$\left(\dfrac23\right)^{-2}$ |
c
|
$\left(\dfrac32\right)^{-2}$ |
d
|
$\left(\dfrac23\right)^{2}$ |
e
|
$-\left(\dfrac23\right)^{-2}$ |
Express $\dfrac {8} {125} $ as a base raised to a negative exponent.
a
|
$-\left(\dfrac 52\right)^{-3}$ |
b
|
$\left(\dfrac 25\right)^{-3}$ |
c
|
$\left(\dfrac 52\right)^{-3}$ |
d
|
$\left(\dfrac 52\right)^{3}$ |
e
|
$-\left(\dfrac 25\right)^{3}$ |