Question

For a function p(x)= x^2-9, what is the inverse function for the domain [0, infinity\

Answer 1

An inverse function is a function that reverses another function, so we have a function called:

$p(x)$

Then, the inverse function will be as follows:

$p^{-1}(x)$

Given that $y = p(x)$, we need to isolate x in terms of y:

$y = x^{2} -9$
∴ $y+9 = x^{2}$

So:

$x=+\sqrt{y+9}$ and $x=-\sqrt{y+9}$

therefore, exchanging variables x and y:

$y=+\sqrt{x+9}$ and $y=-\sqrt{x+9}$
$p^{-1}(x)=+\sqrt{x+9}$ and $p^{-1}(x)=-\sqrt{x+9}$

Which are the figures shown below.