初一数学 帮帮忙` , 求 你们拉

2/（2n-1）*(2n+1)=1/(2n-1)-1/(2n+1)
整体乘二，化简，再整体除二，就哦了，是12/13

(1):2/n(n+2)=n/(2n-1)-1/(2n+1) n
(2):1/3+1/15+1/35+1/63+1/99+1/143
=2(1/3+1/15+1/35+1/63+1/99+1/143)/2
=(2/1×3+2/3×5+2/5×7+2/7×9+2/9×11+1/11×13)/2
=1/1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13
=1/1-1/13
=12/13

(1)2/(2n-1)*(2n+1)=1/(2n-1)-1/(2n+1)
(2)原式=1/2*(1-1/3+1/3-1/5+1/5```+1/11-1/13) =6/13

(1) 2/(2n-1)×(2n+1)=1/(2n-1)-1/(2n+1) n

（2）1/3+1/15+1/35+1/63+1/99+1/143
=2/1×3+2/3×5+2/5×7+2/7×9+2/9×11+1/11×13
=1/1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+1/9-1/11+1/11-1/13
=1/1-1/13
=12/13