x=0,y=-1请问有过程吗(a-b)x -(a+b)y=a+b(a-b)x =a+b+(a+b)y(a-b)x =(a+b)(y+1)x =(a+b)(y+1)/(a-b)(a+b)/(a-b)是不确定的值，只有左右同时为零才相等