does anyone understand this?

**lsnyder** · January 29th 2009, 09:15 PM

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

help please

**Chop Suey** · January 29th 2009, 09:19 PM

Originally Posted by lsnyder

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

help please

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

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

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

**mr fantastic** · January 29th 2009, 09:20 PM

Originally Posted by lsnyder

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

help please

Solve -8 = x^3: x = -2. Therefore f(-2) = -8. Therefore by definition $f^{-1}(-8) = -2$ .

**lsnyder** · January 29th 2009, 09:21 PM

Originally Posted by Chop Suey

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

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

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

yes thank u very much

Thread: does anyone understand this?