# Problem of the Week

## Updated at May 12, 2014 11:49 AM

To get more practice in calculus, we brought you this problem of the week:

How would you differentiate $$\cos{x}-4x$$?

Check out the solution below!

$\frac{d}{dx} \cos{x}-4x$

 1 Use Sum Rule: $$\frac{d}{dx} f(x)+g(x)=(\frac{d}{dx} f(x))+(\frac{d}{dx} g(x))$$.$(\frac{d}{dx} \cos{x})+(\frac{d}{dx} -4x)$2 Use Trigonometric Differentiation: the derivative of $$\cos{x}$$ is $$-\sin{x}$$.$-\sin{x}+(\frac{d}{dx} -4x)$3 Use Power Rule: $$\frac{d}{dx} {x}^{n}=n{x}^{n-1}$$.$-\sin{x}-4$Done-sin(x)-4