# Math Help - evaluate expression

1. ## evaluate expression

given that f(x) = x^3, evaluate [f(x+h) - f(x)]/h

don't know even know how to start

2. ## Re: evaluate expression

$f(x+h)=(x+h)^3$

3. ## Re: evaluate expression

hold, i have to stock up my post count, i cannot view your image

4. ## Re: evaluate expression

What a bothersome irritation, through no fault your own. What I had typed is this:

f(x+h)=(x+h)^3

And knowing that f(x)=x^3 means you should just be able to do a direct substitution, no?

5. ## Re: evaluate expression

let me try

f(x) = x^3

[(x+h)^3 - x^3] / h

[x^3 + 3x^2h + 3xh^2 + h^3 - x^3] / h

[3x^2h + 3xh^2 + h^3] / h

[h(3x^2 + 3xh + h^2)] / h

3x^2 + 3xh + h^2

is this correct? sorry it look very ugly.

btw off topic; what software you use to type your math formula out, i guess it shouldn't be microsoft office or something since i don't know there's a format for that

6. ## Re: evaluate expression

Yeah, looks good. And I use latex, which is a site feature. The "latex help" subforum will get you used to using and appreciating it.