求数列前n项和6/1*3,6/3*5,6/5*7……,6/(2n-1)(2n+1),……
问题描述：
求数列前n项和6/1*3,6/3*5,6/5*7……,6/(2n-1)(2n+1),……
答
数列前n项6/1*3,6/3*5,6/5*7……,6/(2n-1)(2n+1), Sn=6/1*3+6/3*5+6/5*7+……+6/(2n-1)(2n+1), =3(2/1*3+2/3*5+2/5*7+……+2/(2n-1)(2n+1)), =3[1-1/3+1/3-1/5+1/5-1/7+.+1/(2n-1)-1/(2n+1)] =3[1-1...