I think of a number square it and add 2 times the original number.the resuit is 80.find the number

Answer 1

n^2 + 2 n = 80 ... n^2 + 2 n - 80 = 0

factoring ... (n + 10) (n - 8) = 0

n + 10 = 0 ... n = -10

n - 8 = 0 ... n = 8

Answer 2

X^2 + 2x =80
X^2 +2x-80=0
(X+10)(x-8)=0