Answer:
[tex] {(x - 3)}^{2} + 4(x - 3) \\ = (x - 3)((x - 3) + 4) \\ (x - 3)(x - 3+ 4) \\ = (x - 3)(x + 1)[/tex]
(x - 3) is common factor
Imagine you are multiplying or dividing each term by the common factor
[tex] {(x - 3)}^{2} + 4(x - 3) \\ \frac{{(x - 3)}^{2}}{(x - 3)}+(x-3)4\frac{(x - 3)}{(x - 3)}\\(x-3)((x-3)+4)[/tex]
