Think of a number square it,add 2 times to the original number.the result is 80.find the number.

Answer 1

Why not just say,

x^2 + 2x = 80 ?

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

your number was either 8 or -10
both work

Answer 2

Correct

Answer 3

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