-2x + (x-p)(x+p) + (p+1)^2 = (x-p)^2 + 2 | 3. Binom, 1.Binom, 2. Binom
-2x + (x^2 - p^2) + (p^2 + 2p + 1) = ( x^2 - 2px + p^2) + 2
-2x + 2p + 1 = - 2px + p^2 + 2 | +2x - p^2 -2
2p - p^2 - 1 = 2x - 2px = 2x (1 - p)
-(1 -2p + p^2) = 2x - 2px = 2x (1 - p)
-(1-p)^2 = 2x(1-p)
-(1-p)/2 = x
(p-1)/2 = x