Select the correct answer.

If the domain of the function, [tex]f[/tex], is restricted to [tex]x \geq 0[/tex], which function is the inverse of [tex]f[/tex]?

[tex]f(x) = 9x^2 - 12, \quad x \geq 0[/tex]

A. [tex]h(x) = \frac{\sqrt{x - 12}}{3}[/tex]

B. [tex]g(x) = \frac{\sqrt{x + 12}}{3}[/tex]

C. [tex]p(x) = \frac{\sqrt{x - 12}}{9}[/tex]

D. [tex]q(x) = \frac{\sqrt{x + 12}}{3}[/tex]



Answer :

To find the inverse function of [tex]\( f(x) = 9x^2 - 12 \)[/tex] for [tex]\( x \geq 0 \)[/tex], we need to follow a series of steps to express [tex]\( x \)[/tex] in terms of [tex]\( y \)[/tex], and then swap [tex]\( x \)[/tex] and [tex]\( y \)[/tex] to get the inverse function.

1. Start with the given function
[tex]\[ y = 9x^2 - 12 \][/tex]

2. Add 12 to both sides of the equation to isolate the term involving [tex]\( x \)[/tex]
[tex]\[ y + 12 = 9x^2 \][/tex]

3. Divide both sides by 9 to express [tex]\( x^2 \)[/tex] in terms of [tex]\( y \)[/tex]
[tex]\[ \frac{y + 12}{9} = x^2 \][/tex]

4. Take the square root of both sides to solve for [tex]\( x \)[/tex]. Since the domain is restricted to [tex]\( x \geq 0 \)[/tex], we only take the positive root.
[tex]\[ x = \sqrt{\frac{y + 12}{9}} \][/tex]

5. To express the inverse function, swap [tex]\( x \)[/tex] and [tex]\( y \)[/tex]
[tex]\[ f^{-1}(x) = \sqrt{\frac{x + 12}{9}} \][/tex]

This means that the inverse function is
[tex]\[ f^{-1}(x) = \frac{\sqrt{x + 12}}{3} \][/tex]

Looking at the given options:
A. [tex]\(h(x)=\frac{\sqrt{x-12}}{3}\)[/tex]
B. [tex]\(g(x)=\frac{\sqrt{x+12}}{3}\)[/tex]
C. [tex]\(p(x)=\frac{\sqrt{x-12}}{9}\)[/tex]
D. [tex]\(q(x)=\frac{\sqrt{x+12}}{}\)[/tex]

The correct inverse function that matches our derived form [tex]\( \frac{\sqrt{x + 12}}{3} \)[/tex] is option B.

Therefore, the correct answer is:
[tex]\[ \boxed{2 \text (This corresponds to option B)} \][/tex]