Question

-x^2 + 4x = 2

do you have to factor out a -1 before you complete the square?
and whats the answer in vertex form?

Answer 1

I would change the sign by multiplying by -1 and move the 2 to the left side to obtain x^2 -4x +2 = 0 then factor *(it's a perfect square) and solve for x.