21-3/4-4/15-4/35-4/63-4/99-4/143-4/195-4/225
问题描述:
21-3/4-4/15-4/35-4/63-4/99-4/143-4/195-4/225
21-4/3-4/15-4/35-4/63-4/99-4/143-4/195-4/225应该是这样!!
答
原式=21-4/(1*3)-4/(3*5)-……-4/(15*17)
=21-2[1-1/3+1/3-1/5……+1/15-1/17]
=21-32/17
=325/17
你可能是抄错了,最后一个数应该是225