We have

P(x) = (x-2)*(x^2+2*x-2) .

A product is zero if and only if one of the factors is zero. (x-2) is zero for x=2; this we know already. The remaining zeros of P(x) must be those x's for which the second factor is zero. That is, solutions to the equation:

x^2+2*x-2 = 0 .

The latter equation is quadratic. You should be able to solve it.