(3a-6b)/a+b-(5a-6b/a-b)-(4a-5b/a+b)-(7a-8b/b-a)
=[(3a-6b)-(4a-5b)]/(a+b)-[(5a-6b)-(7a-8b)/(a-b)]
=-(a+b)/(a+b)+2(a-b)/(a-b)
=-1+2=1
第2题题目不对啊
1-1÷(1+10%)=1/11
(x/x-y)-(y/x-y)
=x-y
1/a+1/b=1/a+b
(a+b)ˇ2=ab
b/a+a/b=（aˇ2+bˇ2）/ab=【(a+b)ˇ2-2ab】/ab=-1