1/1×3+1/3×5+1/5×7+.+1/49×51=多少?

问题描述:

1/1×3+1/3×5+1/5×7+.+1/49×51=多少?

1/1×3+1/3×5+1/5×7+.+1/49×51
=1/2*(1-1/3+1/3-1/5+1/5-1/7+------+1/49-1/51)
=1/2*(1-1/51)
=25/51