求数学达人来解答 x²/xy-x/y=(1-x)/y3x/4x+y - x-2y/4x+y=(3x-x-2y)/(4x+y)(1-y/y+x)÷x/y²-x²=(1-y)*(y+x)(y-x)/(y+x)*x=(1-y)(y-x)/x=(y-x-y²+xy)/x