计算:1/2×4+1/4×6+1/6×8+……+1/(2n-4)(2n-2)+1/(2n-2).2n(n为正整数)
1-2 -4 -6…+(-1n+1次方)·n(n为正整数)
1-2+3-4+5-6+……+(-1)n+1n(n为正整数 n+1在上面)
3)1-2+3-4+5-6+…+(-1)^n+1 n(n为正整数)
若n为正整数,求1/n(n+1)+1/(n+1)(n+2)+1/(n+2)(n+3)+1/(n+3)(n+4)+.+1/
1*2+2*3+3*4+4*5+…+n(n+1)(n为正整数)
已知888个连续正整数之和:n+(n+1)+(n+2)+(n+3)+(n+4)+(n+5)+(n+6)+(n+7)+··
计算:1-2+3-4+5-6+...(-1)的(n+1)的次方乘以n,n为正整数
1\n(n+3)+1\(n+3)(n+6)+1\(n+6)(n+9)=1\2 n+18 n为正整数,求n的值
1-2+3-4+5-6+...+n+1n(n为正整数 n+1在上面)
Sn=n(n+2)(n+4)的分项等于1/6[n(n+2)(n+4)(n+5)-(n-1)n(n+2)(n+4)]吗?
计算:1/2×4+1/4×6+1/6×8+……+1/(2n-4)(2n-2)+1/(2n-2).2n(n为正整数)
从键盘输入一个正整数n,计算sum=1/2-2/3+3/4-4/5+…+(n-2)/(n-1)-(n-1)/n