分解因式,得
x²-xy+y-1
=(x²-1)-(xy-y)
=(x+1)(x-1)-y(x-1)
=(x-1)(x-y+1)
但我不知道如何填这个空
要填的话只能填x²-xy+y-1=x²-(xy-y+1)
要帮不上忙抱歉啦