\(a,x^2+2x-y^2+1=\left(x^2+2x+1\right)-y^2=\left(x+1\right)^2-y^2=\left(x-y+1\right)\left(x+y+1\right)\\b,2x-1-x^2=-\left(x^2-2x+1\right)=-\left(x-1\right)^2 \)
b , x2 + 2x \(-\) y2 + 1 = (x + 1 + y)(x + 1 \(-\) y)
c , -x2 + 2x - 1 = -(x2 - 2x + 1) = -(x - 1)2