1. ## Precalc, function composition

f(x)=x^3

f(x+DELTA x) - x/ DELTA x

For some reason,
I can't figure it out.

2. Originally Posted by mishiellie
f(x)=x^3

f(x+DELTA x) - x/ DELTA x

For some reason,
I can't figure it out.
It's not clear what your question is. Also please learn about order of operations and parentheses. I believe your second line is meant to convey

$\dfrac{f(x+\Delta x) - x}{\Delta x}$

Perhaps you missed an f and this should be

$\dfrac{f(x+\Delta x) - f(x)}{\Delta x}$

?

Note that $f(x+\Delta x) = (x+\Delta x)^3$. But if you want further help please ask a clear question.