Question

Which of the following is an x intercept of the function f(x)=x^2-81?

A- -72
B -36
C -9
D -81

Answer 1

x intercept when f(x) = 0
so
x^2-81 = 0
x^2 = 81
x = + 9 and x = -9

Answer
C -9

Answer 2

The correct option is C.

Explanation:

The given function is

`f(x)=x^2-81`

Equate the given function equal to zero, to find the x-intercepts of the function.

`f(x)=0`

`x^2-81=0`

Add 81 both the sides.

`x^2=81`

Taking square root both the sides.

`x=\pm √(81)`

`x=\pm 9`

The x-intercepts of the given function are -9 and 9. Therefore the correct option is C.