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问题: 初中题!求高人解答!!

1/1*2与1-1/2;1/2*3与1/2-1/3;1/3*4与1/3-1/4;
1/4*5与1/4-1/5;1/5*6与1/5-1/6......
1.试用含字母的式子表示这种数量关系。
2.计算1/1*2+1/2*3+1/3*4+......+1/49*50

若 |ab-2|+|b-1|=0,试求1/ab+1/(a+1)(b+1)+1/(a+2)
(b+2)+...1/(a+1995)(b+1995)

解答:

1.. 1/n*(n+1) = 1/n - 1/(n+1)


2.. = 1/1 - + 1/21/2 + 1/2 - 1/3 + 1/3.....
+ 1/49 - 1/50
= 1- 1/50

=49/50

3..|ab-2|+|b-1|=0 所以是0 + 0 =0

a=2 b=1

1/ab+1/(a+1)(b+1)+1/(a+2) +(b+2)+...1/(a+1995)(b+1995)

=1/1*2 + 1/ 2*3 + ....+ 1/1996*1997

=1/2 - 1/1997

= 1995/3994