# How do you simplify ( 3 + i ) ( 3 + i )?

$8 + 6 i$
It is the known square ${\left(a + b\right)}^{2}$. So you apply its formula to this complex number.
$\left(3 + i\right) \left(3 + i\right) = {\left(3 + i\right)}^{2} = {3}^{2} + 2 \cdot 3 i + {i}^{2} = 9 + 6 i - 1 = 8 + 6 i$