谁能教我两道数学题?急呀,现在就要!

1.
1/a-1/b=1
(b-a)/(ab)=1
a-b=-ab
(2a+3ab-2b)/(a-2ab-b)
=[2(a-b)+3ab]/(a-b-2ab)
=(-2ab+3ab)/(-ab-2ab)
=ab/(-3ab)
=-1/3
2.
1/a+1/b=5/(a+b)
(a+b)/(ab)=5/(a+b)
(a+b)²=5ab
a/b+b/a
=(a²+b²)/(ab)
=[(a+b)²-2ab]/(ab)
=(5ab-2ab)/(ab)
=3ab/(ab)
=3