Answer:
(x - 15)(x + 3)
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).