45+1/8+1/12+1/20+1/30+1/42+1/72+1/90=
问题描述:
45+1/8+1/12+1/20+1/30+1/42+1/72+1/90=
这个不是我问的问题,不知哪个小子盗我号问的,100分啊!
答
45+1/8+1/12+1/20+1/30+1/42+1/72+1/90
=45+1/8+1/(3*4)+1/(4*5)+1/(5*6)+1/(6*7)+1/(8*9)+1/(9*10)
=45+1/8+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/8-1/9+1/9-1/10
=45+1/8-1/7+1/8+1/3-1/10
=45+143/420