Consider $2x^{2}+2ax+3a+3x$. Do the grouping $2x^{2}+2ax+3a+3x=\left(2x^{2}+2ax\right)+\left(3a+3x\right)$, and factor out $2x$ in the first and $3$ in the second group.
$$2x\left(x+a\right)+3\left(x+a\right)$$
Factor out common term $x+a$ by using distributive property.
