計算:(X的平方-2X+1-Y)除以(X+Y-1)

計算:(X的平方-2X+1-Y)除以(X+Y-1)

x^-2x+1-y^2=(x-1)^2-y^2=(x-y-1)(x+y-1)(x^-2x+1-y^2)/(x+y-1)=x-y-1