已知x/y=2/7,求分式x2-3xy+2y2/x2-2xy+y2的值

已知x/y=2/7,求分式x2-3xy+2y2/x2-2xy+y2的值
已知x/y=2/7,求分式x2-3xy+2y2/x2-2xy+y2的值

已知x/y=2/7,求分式x2-3xy+2y2/x2-2xy+y2的值
x2-3xy+2y2/x2-2xy+y2
分子分母同时除以y²得
原式=[(x/y)²-3(x/y)+2]/[(x/y)²-2(x/y)+1]
=(4/49-6/7+2)/(4/49-4/7+1)
=(4-42+98)/(4-28+49)
=60/25
=12/5

结果与x,y的具体值无关 对于这类问题你直接带入特值求解即可 带入x=2,y=7 得答案12/5