Use a quadratic equation to find two numbers with a sum of 12 and a product of -84

Answer 1

x+y =12

y = 12-x

xy = -84

x(12-x) = -84

12x - x^2= -84

x^2 -12x -84 = 0

x^2 -12x + 36 = 84 + 36

(x-6)^2 = 120

x-6 = 2sqr30

x = 6 + or - 2sqr30

x = about 6 + or - 11 = -5, or 17

y = about 17 or -5

x+y =12

xy =-85, that's close, slight error due to rounding

It's also possible there was a typo in the problem and it should have said the product is -85