# How do you factor 7x^2-847?

Feb 17, 2017

You first try to divide $847 \div 7 = 121$
$= 7 \cdot \left({x}^{2} - 121\right)$
Notice that $121 = {11}^{2}$ and you get the special product for the difference of two squares: ${a}^{2} - {b}^{2} = \left(a + b\right) \left(a - b\right)$:
$= 7 \left(x + 11\right) \left(x - 11\right)$