Answer:
Step-by-step explanation:
b² - 4b - 12 = b² - 6b + 2b - 2*6
=b*(b -6) + 2*(b - 6)
= (b - 6) (b + 2)
b² - 4b - 12 = 0
(b - 6) (b + 2) = 0
b - 6 = 0 or b + 2 = 0
b = 6 or b = -2
