How do you simplify (3² + 3)²?

${\left({3}^{2} + 3\right)}^{2} = 144$
${\left({3}^{2} + 3\right)}^{2} = {\left({3}^{2} + 3 \times 1\right)}^{2}$
= ${\left(3 \times \left(3 + 1\right)\right)}^{2}$
= ${\left(3 \times 4\right)}^{2} = {12}^{2} = 144$