初二数学分式通分，要有过程x-y/2x+2y与xy/(x+y)2 2mn/4m^-9与2m-3/2m+3 要有过程

x-y/2x+2y与xy/(x+y)2 分母的最大公倍数是2(x+y)^=(2x+2y)(x+y) 所以x-y/2x+2y=(x-y)(x+y)/2(x+y)^ xy/(x+y)2=2xy/2(x+y)^ 2mn/4m^-9与2m-3/2m+3 分母的最大公倍数是4m^-9=(2m+3)(2m-3) 所以 2mn/4m^-9不变 2m-3/2m+3=(2m-3)(2m-3)/(2m+3)(2m-3) =4m^-12m+9/4m^-9

1. x-y/(2x+2y)= x-y/[(x+y)2] . xy/[(x+y)2] 分母都为 [(x+y)2] 2.因为4m^2-9=(2m+3)(2m-3), 所以只需要把第二个分式分子分母同乘2m-3即可，即： 前式保持不变，[(2m-3)(2m-)]/[(2m+3)(2m-3)]= (2m-3)^2/(4m^2-9)

1.x-y/2（x+y)=(x-y)(x+y)/2(x+y) xy/(x+y)=2xy/2(x+y)
2.2mn/4m-9=2mn/(2m-3)(2m+3) 2m-3/2m+3=(2m-3)/(2m-3)(2m+3)
这么辛苦打不容易啊，望楼主采纳