# How do you factor x^2 + 13x + 36 ?

May 24, 2015

$\left(x + 4\right) \left(x + 9\right) = 0$

Explanation::

$\left(x + 4\right) \left(x + 9\right)$
$x \text{ times } x = {x}^{2}$
$x \left(9\right) + x \left(4\right) = 13 x$
$4 \text{ times } 9 = 36$
= ${x}^{2} + 13 x + 36$

May 24, 2015

${x}^{2} + 13 x + 36 =$ (x - p)(x - q).
Find p, and q, knowing sum = b = 13 and product c = 36. Compose factor pairs of 36-> (2, 18)(2, 12)(4, 9). this last sum is 9 = b. Then p = 4 and q = 9

y = (x + 4)(x + 9)