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问题: 数学问题,急急急!!!请帮忙,谢谢!!!

1/3+1/15+1/35+1/63+......+1/(2n-1)(2n+1)
注:"/"是分号
请写出过程,谢谢!!

解答:

1/3+1/15+1/35+1/63+......+1/(2n-1)(2n+1)
=1/2[(1-1/3)+(1/3-1/5)+(1/5-1/7)+...+(1/(2n-1)-1/(2n+1))]
=1/2[1-1/3+1/3-1/5+1/5-1/7+...+1/(2n-1)-1/(2n+1)]
=1/2[1+(-1/3+1/3)+(-1/5+1/5)+(-1/7+...+1/(2n-1))-1/(2n+1)]
=1/2[1-1/(2n+1)]
=n/(2n+1)