Question

2乘4分之1加4乘6分之1加6乘8分之1加.98乘100分之1 怎么算 简便算法~

Answer 1

利用公式：2/n(n+1)(n+2)=1/n(n+1)-1/(n+1)(n+2)

1/(4×5×6)+1/(5×6×7)+…+1/(98×99×100)

=1/2[1/4*5-1/5*6+1/5*6-1/6*7+.+1/98*99-1/99*100]

=1/2(1/20-1/9900)

=73/2475