What is the factored form of x2 - 12x - 45?

(x - 15) (x + 3)

Step-by-step explanation:

Factors of 45 include 5 and 9, 3 and 15, 1 and 45, and so on.

Note that 3*15 = + 45; this is not what we wanted. Thus, try (-3) * 15 = - 45.

Do - 3 and 15 combine to yield - 12? No. Thus drop (-3) (15) and try (3) (-15).

Do 3 and - 15 combine to yield - 12? YES

Therefore, the factored form of x² - 12x - 45 is (x - 15) (x + 3).