# How do you simplify 2cos^2x + cosx -3?

Nov 13, 2015

Simplify f(x) = 2cos^2 x + cos x - 3

f(x) = (cos x - 1)(2cos x + 3)

#### Explanation:

$f \left(x\right) = 2 {\cos}^{2} x + \cos x - 3.$
Since a + b + c = 0, the 2 factors are: $\left(\cos x - 1\right)$ and
$\left(\cos x + \frac{c}{a}\right) = \left(\cos x + \frac{3}{2}\right)$
f(x) = (cos x - 1)(2cos x + 3)