Answer: x = {-12, 6}
Explanation:
Need to find two numbers whose product equals the c-value of -72 and sum equals the b-value of +6.
x² + 6x - 72 = 0
∧
-1 +72 = 71
-2 +36 = 34
-3 +24 = 21
-4 +18 = 14
-6 +12 = 6 --> this works!
(x - 6)(x + 12) = 0
x - 6 = 0 and x + 12 = 0
x = 6 and x = -12