Question

已知a=1.b=2.求ab分之一+(a+1)(b+1)分之一+(a+2)(b+2)分之一+………+（a+2001)(b+

Answer 1

=1/1×2+1/2×3+1/3×4+……+1/2002×2003

=1-1/2+1/2-1/3+1/3-……-1/2002+1/2002-1/2003

=1-1/2003

=2002/2003

看其中的一个如

1/49×50

=(50-49)/49×50

=50/49×50-49/49×50

=1/49-1/50