计算1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90的值等于?
问题描述:
计算1/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90的值等于?
答
1/2=1-1/21/6=1/2-1/31/12=1/3-1/41/20=1/4-1/51/30=1/5-1/61/42=1/6-1/7……1/90=1/9-1/101/2+1/6+1/12+1/20+1/30+1/42+1/56+1/72+1/90=(1-1/2)+(1/2-1/3)+(1/3-1/4)+……+(1/9-1/10)=1-1/10=9/10...