Question

What is the positive root of the equation x 2 - 2x = 120

Answer 1

x²-2x=120
x²-2x-120=0
(x+10)(x-12)=120
x=-10, 12

Answer 2

There is a shortcut.

It can be converted to (x-1)^2 = 121

If you know 121 = 11^2

Then you get x-1 = 11 or -11, so x = 12 or -10