有几道数学题不会做哇.谁来帮帮我.明天要交的.

（1）1/2x-1/(x+y)*[(x+y)/2x-x-y]
=1/2x-1/(x+y)*[(x+y)/2x-2x(x+y)/2x]
=1/2x-1/(x+y)*[(x+y)-2x(x+y)]/2x
=1/2x-1/(x+y)*(x+y)(1-2x)/2x
=1/2x-(1-2x)/2x
=[1-(1-2x)]/2x
=2x/2x
=1
（2）[1/(m+n)²-1/(m-n)²]÷[(1/(m+n）-1/(m-n)]
=[(m-n)²-(m+n)²]/[(m+n)²*(m-n)²]÷[(m-n)-(m+n)]/[(m+n)(m-n)]
=-4mn/[(m+n)²*(m-n)²]÷(-2n)/[(m+n)(m-n)]
=-4mn/[(m+n)²*(m-n)²]*[(m+n)(m-n)]/(-2n)
=2m/[(m+n)(m-n)]
=2m/(m²-n²)
（3）{2/3x-2/(x+y)*[(x+y)/3x-x-y]}÷(x-y)/y
={2/3x-2/(x+y)*[(x+y)(1-3x)/3x]}÷(x-y)/y
={2/3x-2(1-3x)/3x}*y/(x-y)
=[2-2(1-3x)]/3x*y/(x-y)
=6x/3x*y/(x-y)
=2y/(x-y)

这什么题啊，都是直接带进括号里就出来答案了啊

(1)=1/2x-(1/x+y)*(x+y)(1-2x)/2x=1/2x-(1-2x)/2x=1
(2)=[1/(m+n)+1/(m-n)][1/(m+n)-1/(m-n)]÷[(1/m-n）-1/(m-n)]=1/(m+n)+1/(m-n)=2m/(m+n)(m-n)
(3)=[2/3x-2/(x+y)[(x+y)(1/3x-1)]]÷(x-y)/y=[2/3x-2(1/3x-1)]÷(x-y)/y=2y/(x-y)