# Thread: find the derivative of function using

1. ## find the derivative of function using

$f(x+h)-f(x)/h$

1) $f(x)=5x^3$

2. $f(x+h) = 5(x+h)^3 = 5(x^3+3x^2h+3xh^2+h^3)$

$f(x) = 5x^3$

Compute

$f(x+h) - f(x) = 5x^3 + 15x^2h+15xh^2+5h^3 - 5x^3 = 15x^2h+15xh^2+5h^3$

Don't forget to use the limit notation in your definition:

$\lim_{h\to 0} \frac{f(x+h)-f(x)}{h}=\lim_{h\to 0} \frac{15x^2h+15xh^2+5h^3}{h}=\lim_{h\to 0}15x^2+15xh+5h^2=...$

Good luck!