# How do you factor 16g^2-72g+81?

${\left(4 g - 9\right)}^{2}$
$16 {g}^{2} - 72 g + 81 = {\left(4 g\right)}^{2} - 2 \cdot 4 g \cdot 9 + {9}^{2}$
$q \quad = {\left(4 g - 9\right)}^{2}$