Originally Posted by

**Nforce** It's pretty straight forward procedure.

We have a function:

$\displaystyle f(x) = 2x^2 + 3x$

To get the derivative, we use the limit definition.

$\displaystyle \lim_{h\to\0}\frac{f(x + h) - f(x)}{h}$

$\displaystyle \lim_{h\to\0}\frac{2(x+h)^2 + 3(x+h) - 2x^2 +3x}{h}$

$\displaystyle \lim_{h\to\0}\frac{2x^2 + 2xh + h^2 + 3x + 3h - 2x^2 +3x}{h}$

$\displaystyle \lim_{h\to\0}\frac{4xh + 2h^2 +3h + 6x}{h}$

But how can I get rid of **6x** in the numerator? Because that's the problem, I can't get the proper derivative, if the **6x** is in the numerator.