计算1/3×5+1/5×7+1/7×9+···+1/21×23,3×5是分母,5×7是分母,7×9是分母,···21×23是分母

问题描述:

计算1/3×5+1/5×7+1/7×9+···+1/21×23,3×5是分母,5×7是分母,7×9是分母,···21×23是分母

1/3×5+1/5×7+1/7×9+···+1/21×23
=1/2×(1/3-1/5+1/5-1/7+……+1/21-1/23)
=1/2×(1/3-1/23)
=1/2×20/69
=10/69是1/3×5+1/5×7+1/7×9+···+1/21×23,你是不是看错了是啊,你看看,我算的就是1/3×5+1/5×7+1/7×9+···+1/21×23=1/2×(1/3-1/5+1/5-1/7+……+1/21-1/23)=1/2×(1/3-1/23)=1/2×20/69=10/69