1x2+2x3+3x4+.+100x101=?结果

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1x2+2x3+3x4+.+100x101=?结果
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1x2+2x3+3x4+.+100x101=?结果
1x2+2x3+3x4+.+100x101=?
结果

1x2+2x3+3x4+.+100x101=?结果
x2+2x3+3x4+.+100x101=
的通项公式An=n*(n+1)=n²+n
前n项和Sn=(1²+2²+……+n²)+(1+2+……+n)
=n（n+1)(2n+1)/6+n(n+1)/2
所以
1x2+2x3+3x4+.+100x101=S（100）
=100*101*201/6+100*101/2=343400

数列求和 答案如楼上

1/1x2+1/2x3+1/3x4+1/4x5.1/9x10简算 计算：1/1x2+1/2x3+1/3X4+...+1/9x10=? 1X2/1+2X3/1+3X4/1+……+9X10/1=_____ 计算：1/1x2+1/2x3+1/3X4+...+1/9x10=? -1/1x2-1/2x3-1/3x4-.-1/9x10 1x2/1+2x3/1+3x4/1+……+9x10/1 1/(1x2)+1/(2x3)+1/(3x4)+.+1/(9x10) 1X2/1—2X3/1—3X4/1—...—9X10/1=? 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11 1x2+2x3+3x4+.+100x101= 1x2+2x3+3x4+.+100x101=?结果 已知:x1=1/2+1/3,x2=1/3+1/4,x3=x2+x1,x4=x3+x2.,x10=x9+x8,求：x7/x1+x2+...+x10 1/1x2+1/2x3+1/3x4+……+1/9x1o= 1/1x2-1/2x3-1/3x4……-1/1x2+1/2x3+1/3x4+……+1/9x1o=1/1x2-1/2x3-1/3x4……-1/9x10= 用克拉默法则解下列方程组 x1-2x2+3x3-4x4=4 x2-x3+x4=-3 x1+3x2+2x4=1 -7x2+3x3+x4=3x1-2x2+3x3-4x4=4x2-x3+x4=-3 x1+3x2+2x4=1 -7x2+3x3+x4=3 解方程组X1-2x2+3x3-x4=1,3x1-x2+5x3-3x4=2,2x1+x2+2x3-2x4=3 写出方程组2*x1+x2-x3+x4=1,x1+2*x2+x3-x4=2,x1+x2+2*x3+x4=3的通解? 求非齐次线方程组的通解 ：2x1+x2-x3+x4=1 x1+2x2+x3-x4=2 x1+x2+2x3+x4=3 具体写出方程组：2x1+x2-x3+x4=1;x1+2x2+x3-x4=2;x1+x2+2x3+x4=3的通解