# Thread: Finding a second derivative

1. ## Finding a second derivative

I need to find the integral from 1-4 of xf''(x)dx given that f(1)=2, f(4)=7, f'(1)=5, and f'(4)=3. I'm not sure how to begin. When I've done this sort of thing before I always had the function.

2. $\int x \cdot f''(x) \, dx$

$u = x$
$du = dx$

$dv = f''(x) \, dx$
$v = f'(x)$

$x \cdot f'(x) - \int f'(x) \, dx = x \cdot f'(x) - f(x)$

now use the FTC to determine the value of the definite integral.

3. OK, I get it. That's kind of fun! Thanks again for your help.