Question

Which equation is the inverse of y = 9x2 - 4?

Answer 1

Answer:

The inverse will be:

$y' = \frac{\sqrt{x+4}}{3}$

Step-by-step explanation:

In order to find the inverse of the equation, we do a variable change, since we are finding the inverse, :

$f(x) = 9x^{2} - 4$

$y = 9x^{2} - 4$

$x = 9y' ^{2} - 4$

Now solve for y'.

First add 4 in both sides of the equation and change to the left y'.

$x + 4= 9y'^{2} - 4+4$

$9y'^{2}$ = x + 4

Second divide by 9

$9y'^{2}$/9 = (x + 4)/9

$y'^{2}$ = (x + 4)/9

Now you will have to clear y, with the square root.

$[tex]y'^{\frac{2}{2}} = \sqrt{x + 4} / \sqrt{9}$[/tex] =

Simplifying terms

$y' = \frac{\sqrt{x+4}}{3}$

$f^{-1}(x) = \frac{\sqrt{x+4}}{3}$

You can check the answer by doing the evaluation of the following equation:

(f o $f^{-1}$ ) (x)

substitute the equation for y' or inverse function $f^{-1}$

f($\frac{\sqrt{x+4} }{3}$)

Now substitue the value into f(x)

You will have

$= 9(\frac{\sqrt{x+4} }{3}} )^{2} - 4\\\\Solving\\\\9(\frac{{x+4} }{9}} ) - 4$

=x