# How do you factor 4-49z^2?

Nov 27, 2015

$\left(2 + 7 z\right) \left(2 - 7 z\right)$

#### Explanation:

The expression if the difference of two squares

$\left(a + b\right) \left(a - b\right) = {a}^{2} - a b + a b - {b}^{2} = {a}^{2} - {b}^{2}$

In this case

$a = 2$, ${a}^{2} = 4$

$b = 7 z$, ${b}^{2} = 49 {z}^{2}$