1/2x4+1/4x6+1/6x8+……+1/(2n-4)(2n-2)+1/(2n-2)x2nn为正整数!要写出计算过程 和答案

1/2x4+1/4x6+1/6x8+……+1/(2n-4)(2n-2)+1/(2n-2)x2nn为正整数!要写出计算过程 和答案
1/2x4+1/4x6+1/6x8+……+1/(2n-4)(2n-2)+1/(2n-2)x2n
n为正整数!
要写出计算过程 和答案

1/2x4+1/4x6+1/6x8+……+1/(2n-4)(2n-2)+1/(2n-2)x2nn为正整数!要写出计算过程 和答案
1/2x4+1/4x6+1/6x8+……+1/(2n-4)(2n-2)+1/(2n-2)x2n
=1/2{(1/2-1/4)+(1/4-1/6)+(1/6-1/8)...+[1/(2n-2)-1/2n]}
=1/2*(1/2-1/2n)
=1/4-1/(4n)