更新时间2018-06-07 21:07:34
原式=4/15+4/35+4/63+4/99+4/11
=4×1/2×(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11)+4/11
=2×(1/3-1/11)+4/11
=2×8/11+4/11
=16/11+4/11
=20/11
十五分之四加三十五分之四加六十三分之四加九十九分之四加十一分之四
=2*(2/15+2/35+2/63+2/99+2/11)
=2*(1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+2/11)
=2*(1/3+1/11)
=2*14/33
=28/33