Factor the expression by grouping. First, the expression needs to be rewritten as $x^{2}+ax+bx+36$. To find $a$ and $b$, set up a system to be solved.
$$a+b=12$$ $$ab=1\times 36=36$$
Since $ab$ is positive, $a$ and $b$ have the same sign. Since $a+b$ is positive, $a$ and $b$ are both positive. List all such integer pairs that give product $36$.
