Derivative f(x)=x^3, f(a+h)-f(a)/h

[alexhenderson]

Homework Statement

f(x)=x^3 f(a+h)-f(a)/h

Homework Equations

I am having troubles at the moment with the process, I am getting a^3+3a^2h+3ah^2+h^3-a^3.

The Attempt at a Solution

I have simplified the equation further and got 3a^2+3ah+h^2, help would be appreciated. Thanks for reading.

 

[Lily@pie]

You are trying to look for the derivative? Or just simplifying the equation?

You will need to get the limit as h approaches 0 for derivative.

 

[alexhenderson]

You are trying to look for the derivative? Or just simplifying the equation?

I already know the derivative, so just simplifying the equation.

 

[Lily@pie]

If you just need to simplify the equation f(a+h)-f(a)/h, then you have already done so by getting 3a^2+3ah+h^2 as the answer.

 

[alexhenderson]

If you just need to simplify the equation f(a+h)-f(a)/h, then you have already done so by getting 3a^2+3ah+h^2 as the answer.

http://img192.imageshack.us/f/derivative.jpg/" Can you check my math? Please.

 

[Lily@pie]

It should be fine... According to my education system ><

For me, i'll straight away use the definition of derivative
f'(x) = lim_h->0 f(a+h)-f(a)/h

Would not try to derive all the way from (f(b)-f(a))/(b-a), too time consuming.

 

[alexhenderson]

Ok, thank you.