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

Use the definition of the derivative as a limit to determine the slope of the

tangent line to f(x) at x = 1

I know the rule is limit as h goes to 0 $\displaystyle f(x+h) - f(x)\over {h}$

But how do I rearrange this one so the answer isn't 0?