帮忙找十来道分式的计算题

1.计算（ab+a2)÷a2+2a3b+b2/ab ×a+b/a2
2.以知x+y=8,xy=-18
求x2+y2 1/x2 + 1/y2
3.以知a-b≠0 2a-3b=0
求2a+b/a-b
4.计算2/(x+1)(x+3)+2/(x+3)(x+5)+、、、+2/(x+1997)(x+1999)
5.以知x-3/(x+1)(x-1)=a/s+1 + b/x-1 求a\b的值
6.设a+b+c=0
证明：a(1/b +1/c)+b(1/c +1/a)+c(1/a + 1/b)+3=0
7. x-2/x2-y2 + y-2/y2-x2
8.已知a+1/a=b+1/(b-1)-2且a-b+2≠0，试求ab-a+b的值。
9.[(2+3y/x)/(2-3y/x)]*[(x/3-y/2)/(x/3+y/2)]
10.(x-3/2x-4)/[(5/x-2)-x-2]