#### Answer

$x^{2} + 12x + 36$.

#### Work Step by Step

In the equation $x^{2}$ + $bx$ + $c$, we need to find $c$. To do so we must divide $b$ by $2$.
With $b=12$, then
$\dfrac{b}{2} = \dfrac{12}{2} = 6$
After $b$ is divided by $2$, square the result to obtain:
$\left(\frac{b}{2}\right)^2=6^2=36$
Therefore, the missing term is $36$.