input output what is the rule

Question

if the output is 198 and the rule is x times x -2 what is the input?

Answer 1

x(x-2) = 198

x^2 -2x - 198 = 0

x^2 -2x + 1 = 199

x -1 = +/-sqr199

x = Input = 1+sqr199 or 1-sqr199