Question

What is the value of xx) = 9^x when x= -2?

A. 1/81

B. 81

C. 1/81

D. 18​

Answer 1

C.
`9^(-2) = (1)/(81)`

Explanation:

Given

`9^(x)`

Required

Find the expression where x - 2

`9^(x)`

Substitute 2 for x

`9^(-2)`

From law of indices which states

`a^(-b) = (1)/(a^b)`

So, the expression becomes

`9^(-2) = (1)/(9^2)`

Expand the denominator

`9^(-2) = (1)/(9 * 9)`

`9^(-2) = (1)/(81)`

Hence,
`9^(x)` is
`(1)/(81)` when x = 2