Question

计算(-1×1/2)+(-1/2*1/3)+...+(-1/2012*1/2013)

Answer 1

原式=（-1）*[(1*1/2)+(1/2*1/3)+...+(1/2012*1/2013)]

=(-1)*[(1-1/2)+(1/2-1/3)+...+(1/2012-1/2013)]

=(-1)*(1-1/2013)

=-2012/2013