# Thread: How do you find the second derivative?

1. ## How do you find the second derivative?

For example,
if f(x)=x^9+4x^3+3x, find the second derivative f " (x).

im so confused...i honestly have no idea

2. $f(x)=x^9+4x^3+3x$
to find the second derivative, you simply take the first derivative, then from that result do the exact same thing to get the second.

$f'(x)= 9x^8 + 12x^2 +3$
$f''(x) = 72x^7 + 24x$

3. Remember the derivative of a function f(x) is another function (The 'Gradient function'), denoted f '(x), so all you do is take the derivative of this function to get the 'second derivative,' f''(x)....so it's as easy as that - differentiate twice. Think you can do it now?

edit: beaten to the mark

4. yes....thank you both very much