已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
问题描述：
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
答
因为(x-y)/(x+y)=3,则(x＋y)/(x－y)＝1/3
则5(x-y)(x+y)-(x+y)/2(x-y)
＝5*3 -1/(3*2)
=15-1/6
=89/6