1/2×5+1/3×6+1/4×7。。。1/7×10

显示全部楼层 · 2012-11-8 22:54:00

1/2×5+1/3×6+1/4×7。。。1/7×10=1/3（1/2-1/5）+1/3（1/3-1/6）+1/3（1/4-1/7）+1/3（1/5-1/8）+1/3（1/6-1/9）+1/3（1/7-1/10）=1/3（1/2-1/5+1/3-1/6+1/4-1/7+1/5-1/8+1/6-1/9+1/7-1/10）=1/3（1/2+1/3+1/4-1/8-1/9-1/10）=1/3*（13/12-121/360）=1/3*（390/360-121/360）=1/3*269/360=269/1080...

千问 · 2012-11-8 22:54:00

1/2×5+1/3×6+1/4×7。。。1/7×10=(1/2-1/5+1/3-1/6+1/4-1/7+……+1/7-1/10）÷3=（1/2+1/3+1/4-1/8-1/9-1/10）÷3=（13/12-121/360）÷3=269/360÷3=269/1080...

千问 · 2012-11-8 22:54:00

5/2+2+7/4+8/5+3/2+10/7=6+7/4+10/7=6+89/28...