2/15+2/35十2/63十2/99=

问题描述:

2/15+2/35十2/63十2/99=

2/15+2/35十2/63十2/99
=2/3×5+2/5×7+2/7×9+2/9×11
=1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11
=1/3-1/11
=8/33