1. The problem statement, all variables and given/known data Factor the polynomial x^2 - 4x + 4 -4y^2 completely. 2. Relevant equations 3. The attempt at a solution Rearranging, I get x^2 - 4y^2 - 4x + 4 Then, I know that it is equal to (x -2y)(x+2y) - 4(x-1) and that is my final answer. but, my teacher only considered the answer : (x-2)^2 - 4y^2 then, (x-2+2y)(x-2-2y) ---- I know how he got HIS factored form, but is it only the right answer? Is my answer wrong? Isn't it that the polynomial is completely factored if it can no longer be factored(prime) ? Can there be one and only one factored form for a polynomial? If so, how do you judge if it is the right factored form of the polynomial? Please help me. I'm really confused. Thanks in advance!