观察下列算式,再计算:1/2-1/3=1/6,1/3-1/4=1/12,1/4-1/5=1/201/6+1/12+1/20+1/42+1/56+1/72+1/90

问题描述:

观察下列算式,再计算:1/2-1/3=1/6,1/3-1/4=1/12,1/4-1/5=1/20
1/6+1/12+1/20+1/42+1/56+1/72+1/90