2+4+6=12=3X4;2+4+6+8=20=4X5;……,则n个偶数只和应为2+4+6+8+……=().则2+4+6
2+4=6=2×3;2+4+6=12=3×4; 2+4+6+8=20=4×5;……,则;连续n个偶数之和应为2+4+6+
从2开始,连续的偶数相加,如下:2=1x2 2+4=6=2x3 2+4+6=12=3x4 2+4+6+8=20=4x5
1x2+2x3+3x4+4x5+……+199x200的和是奇数还是偶数?
1分解因式:2x4-x3-13x2-15=?2.分解因式:x5+x4+x3+x2+x+1=?3分解因式:x4-4x2+6
sn=(2-3x5^-1)+(4-3x5^-2)+…+(2n-3x5^-n)要详解答案,急用!
简单线代题///X1+X2+X3+X4+X5=13X1+2X2+X3+X4+3X5=0 X2+2X3+2X4+6X5=3
求线性方程组的全部解x1+x2-3x4-x5=2x1-x2+2x3-x4=14x1-2x2+6x3+3x4-4x5=82
求齐次线性方程组x1+2x2+x3+x4+x5=1 2x1+4x2+3x3+x4+x5=2 -x1-2x2+x3+3x4
观察下列各式 2=1x2.2+4=6=2x3,2+4+6=12+3x4,2+4+6+8=20=4x5…… 猜想:(1)2
设总体X~N(12,4),有n=5的样本X1,X2,X3,X4,X5,求P{min(X1,X2…,X5)
(2X2)/1X3+(4X4)/(3X5)+(6X6)/(5X7)+...+(20X20)/(19X21)==?
2=1x2 2+4=6=2x3 2+4+6=12=3x4 2+4+6+8=20=4x5