:2/1×+2/3×5+2/5×7+2/7×9+.+2/33×55

问题描述:

:2/1×+2/3×5+2/5×7+2/7×9+.+2/33×55
能简便的要简便

=2(1/1*3+1/3*5+...+1/33*35)
=2[1/2*(1-1/3)+1/2*(1/3-1/5)+...+1/2*(1/33-1/35)
=1-1/35
=34/35