# The steps to find f''(x)=x^4 - 4x^3

• March 25th 2009, 05:50 PM
calcconfused
The steps to find f''(x)=x^4 - 4x^3
i have the answer as f''(x)=12x^2 - 24x and i am not sure how/why i have that
• March 25th 2009, 05:54 PM
Pinkk
Do you mean $f(x)=x^{4}-4x^{3}$? If so:

$f'(x)=4x^{3}-12x^{2}$
$f''(x)=12x^{2}-24x$
• March 25th 2009, 05:59 PM
calcconfused
Quote:

Originally Posted by Pinkk
Do you mean $f(x)=x^{4}-4x^{3}$? If so:

$f'(x)=4x^{3}-12x^{2}$
$f''(x)=12x^{2}-24x$

thats what i thought. i think my professor made an error. the original is f(x) = x^4 - 4x^3. he said then that f''(x) = 12x^2 - 24x. that made no sense to me...
• March 25th 2009, 06:05 PM
Pinkk
Just take the derivative, then take the derivative of the derivative.