Question

观察下列等式：1乘2分之1=1-2分之1

1/1×2+1/2×3+1/3×4+…+1/2009×2010

Answer 1

1/1×2+1/2×3+1/3×4+…+1/2009×2010

=1-1/2+1/2-1/3+1/3-1/4+……+1/2009-1/2010
=1-1/2010
=2009/2010