Question

（-1*1/2）+（-1/2*1/3）+（-1/3*1/4）+.+(-1/2011*1/2012)+(-1/2012*1

Answer 1

（-1*1/2）+（-1/2*1/3）+（-1/3*1/4）+.+(-1/2011*1/2012)+(-1/2012*1/2013)

=-(1/1×2+1/2×3+1/3×4+……+1/2012×2013)

=-(1-1/2+1/2-1/3+1/3-1/4+1/4-……+1/2012-1/2013)

=-(1-1/2013)

=-2012/2013