1. ## Composite function thread 2?

Evaluate if possible the function at the given value of the independent valuable.

f(x)=x^3

f(x+delta x-f(x)/(delta x)

This is what I did

f(x+delta x)^3-f(x)

I got

(x^2+2(delta)x+delta(x)^2) (x+delta(x))-f(x)

Which then I put into

x^3 + 2 delta(x) * x + delta(x)^2 * x + x^2*delta(x)+2delta(x)delta(x)+delta(x)^3

Which I simplified

x^3 + 2x*delta(x) + x*delta(x)^2 +x^2*delta(x) + 2delta(x)^2 + delta(x)^3-f(x)/(delta x)

But I am stuck any help would be appreciated

2. ## Re: Composite function thread 2?

$\displaystyle \left( {x + \Delta x} \right)^3 = x^3 + 3x^2 \Delta x + 3x\left( {\Delta x} \right)^2 + \left( {\Delta x} \right)^3$

3. ## Re: Composite function thread 2?

Evaluate if possible the function at the given value of the independent valuable.

f(x)=x^3

f(x+delta x-f(x)/(delta x)
$\displaystyle f(x) = x^3$
$\displaystyle f(x+\delta x) = (x + \delta x)^3 = x^3 + 3x^2.\delta x + 3x.(\delta x)^2 + (\delta x)^3$

I hope thing are now more clear to proceed with evaluating $\displaystyle \frac{f(x+\delta x)-f(x)}{\delta x}$