# Simplify cos^2x-4/cosx+2?

If you mean $\frac{{\cos}^{2} x - 4}{\cos x + 2}$ the answer is $\cos x - 2$
(a+b)(a-b)=${a}^{2} - {b}^{2}$ when multiplied out.
So $\frac{{a}^{2} - {b}^{2}}{a + b} = \frac{\left(a + b\right) \left(a - b\right)}{a + b}$
Cancel to get $\left(a - b\right)$