1/2*5+1/5*8+1/8*11+1/11*14+1/14*17=?

问题描述:

1/2*5+1/5*8+1/8*11+1/11*14+1/14*17=?
这些题怎样算?

原式=1/3(1/2-1/5+1/5-1/8+1/8-1/11+1/11-1/14+1/14-1/17)
=1/3*(1/2-1/17)
=1/3*(15/34)
=5/34