# Help , please ! I don't know

• Oct 27th 2008, 01:44 AM
butbi9x
Help , please ! I don't know
if f(x)= x/(x^2 +1)
(a) find f'(x) and f''(x)
(Crying) Check to see that your answers to part (a) are reasonable by comparing the graphs of f, f' and f'' (Headbang)

Help me !
• Oct 27th 2008, 04:10 AM
mr fantastic
Quote:

Originally Posted by butbi9x
if f(x)= x/(x^2 +1)
(a) find f'(x) and f''(x)
(Crying) Check to see that your answers to part (a) are reasonable by comparing the graphs of f, f' and f'' (Headbang)

Help me !

Start by using the quotient rule to get f'(x).

To get f''(x), use the quotient rule to differentiate f'(x).
• Oct 27th 2008, 04:17 AM
butbi9x
huhu
I don't understand (Angry)
• Oct 27th 2008, 04:22 AM
mr fantastic
Quote:

Originally Posted by butbi9x
I don't understand (Angry)

Then go back to your textbook or class notes and revise the quotient rule and the chain rule. Then read my first post again.
• Oct 27th 2008, 04:38 AM
toraj58
if

$\displaystyle h(x) = \frac {f(x)}{g(x)}$

then

$\displaystyle h^\prime(x) = \frac {f^\prime(x)g(x) - g^\prime(x)f(x)}{g^2(x)}$