# How do you factor 4 - 25x^2?

$\left({a}^{2} - {b}^{2}\right) = \left(a - b\right) \cdot \left(a + b\right)$
This form fits the given expression $\left(4 - 25 {x}^{2}\right)$
with ${a}^{2} = {2}^{2}$ and ${b}^{2} = {\left(5 x\right)}^{2}$
so $\left(4 - 25 {x}^{2}\right)$ can be factored as
$\left(2 - 5 x\right) \left(2 + 5 x\right)$