计算:1/2+1/6+1/12+1/20+/+1/30+1/42+1/56+1/72+1/90
问题描述:
计算:1/2+1/6+1/12+1/20+/+1/30+1/42+1/56+1/72+1/90
要意思
答
原式=(2520+840+420+252+180+120+56)/5040=9388/5040