# Math functions of functions.

• Sep 20th 2010, 11:17 AM
pewpew01
Math functions of functions.
Suppose that f(5) = -1, f'(5) = 2, g(5) = 5, g'(5)=-3
find (g/(f^2+g))' (5).

I must be doing something wrong. Because my answer is way off. Or maybe it's because I'm not understanding the notation properly.
• Sep 20th 2010, 11:28 AM
skeeter
Quote:

Originally Posted by pewpew01
Suppose that f(5) = -1, f'(5) = 2, g(5) = 5, g'(5)=-3
find (g/(f^2+g))' (5).

I must be doing something wrong. Because my answer is way off. Or maybe it's because I'm not understanding the notation properly.

quotient rule and chain rule, correct?

$\displaystyle \left(\frac{g}{f^2+g}\right)' = \frac{(f^2+g) \cdot g' - g(2f \cdot f' + g')}{(f^2+g)^2}$

now sub in your given values and determine the derivative at 5
• Sep 20th 2010, 11:33 AM
pewpew01
Oh... right. Chain rule and quotient. How could I forget about it.
kk thanks.