SOLUTION: What two numbers multiplies to -8000 but add to +20?

Question 1023773: What two numbers multiplies to -8000 but add to +20?
Found 2 solutions by Fombitz, msalonga:
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
Use Cramer's rule,

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Answer by msalonga(4) (Show Source): You can put this solution on YOUR website!
eq 1. xy = -8000
eq 2. x+y = 20
from eq 2. y = 20 - x
substituting y to eq. 2
x(20-x) = -8000
20x - x^2 = -8000, rearraging to ax^2 + bx + c = 0
x^2 - 20x - 8000 = 0; a = 1; b = -20; c = -8000
using quadratic formula
x = 100 and -80
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