Question

Which function below is the inverse of f(x) = x2 − 9?

Answer 1

F (x)=y
y=2x-9


X Y
-2 -15 y=2 (-2)-9
y=-4+-9
y=-15

-1 -11 y=2 (-1)-9
y=-2+-9
y=-11

0 -9 y=2 (0)-9
y=0+-9
y=-9

1 -7 y=2 (1)-9
y=2+-9
y=-1

2 -5 y=2 (2)-9
y=4+-9
y=-5

Here is all the work

Answer 2

Let f(x)=y
y=$x^{2} -9$
Make x the subject of the formula;
y+9=$x^{2}$
x=$\sqrt{y+9}$
So, the inverse of the function is thus;
$f^{'} = \sqrt{x+9}$