再次麻烦已知1/2=1-1/2;1/6=1/2x3=1/2-1/3;1/12=1/3x4=1/3-1/4 求:5/6-7/12+9/20-1/30+13/42=?
问题描述:
再次麻烦已知1/2=1-1/2;1/6=1/2x3=1/2-1/3;1/12=1/3x4=1/3-1/4 求:5/6-7/12+9/20-1/30+13/42=?
答
5/6-7/12+9/20-1/30+13/42
=(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5-1/6)+(1/6+1/7)
=1/2+2/6+1/7
=14/42
如果是5/6-7/12+9/20-11/30+13/42
5/6-7/12+9/20-11/30+13/42
=(1/2+1/3)-(1/3+1/4)+(1/4+1/5)-(1/5+1/6)+(1/6+1/7)
=1/2+1/7
=9/14