# How do you differentiate f(x)=x^2-x-x(x-1) using the sum rule?

Dec 13, 2015

$f ' \left(x\right) = 0 , \forall x \in \mathbb{R}$

#### Explanation:

Simplifying function into standard polynomial form by multiplying out the brackets we get

$f \left(x\right) = {x}^{2} - x - {x}^{2} + x$

$\therefore f ' \left(x\right) = 2 x - 1 - 2 x + 1$

$= 0$