# Math Help - does anyone understand this?

1. ## does anyone understand this?

Problem:
f(x)=x^3, find f^-1 (-8)

2. Originally Posted by lsnyder
Problem:
f(x)=x^3, find f^-1 (-8)

$y = x^3 \implies x=\sqrt[3]{y}$

$f^{-1}(x) = \sqrt[3]{x}$

Can you find $f^{-1}(8)$ now?

3. Originally Posted by lsnyder
Problem:
f(x)=x^3, find f^-1 (-8)

Solve -8 = x^3: x = -2. Therefore f(-2) = -8. Therefore by definition $f^{-1}(-8) = -2$.
$y = x^3 \implies x=\sqrt[3]{y}$
$f^{-1}(x) = \sqrt[3]{x}$
Can you find $f^{-1}(8)$ now?