1/2x4+1/4x6+1/6x8+...+1/198x200

1/2x4+1/4x6+1/6x8+...+1/198x200
1/2x4+1/4x6+1/6x8+...+1/198x200

1/2x4+1/4x6+1/6x8+...+1/198x200
1/（2x4）+1/（4x6）+1/（6x8）+...+1/（198x200）
=1/2*(1/2-1/4+1/4-1/6+.+1/198-1/200)
=1/2*(99/200)
=99/400

拆项分解 如1/2*4 = 0.5*(1/2 - 1/4)
。。。。。。
1/n(n+2) = 0.5(1/n - 1/n+2)
最后可得答案0.2475

裂项