1x3＋2x4＋3x5＋4x6……＋100x102＝?

1x3＋2x4＋3x5＋4x6……＋100x102＝? 1/1x3+1/2x4＋1/3x5＋1/4x6＋……＋1/19x21 急, 1x2÷1＋2x3÷1＋3x4÷1＋4x5÷1＋5x6÷1等于? 1x1－2x2＋3x3－4x4＋5x5－6x6.－100x100＋101x101 1/1x3+1/2x4+1/3x5+1/4x6+...+1/10x12 为什么1/2+5/6+11/12+19/20+…………＋89/90 的规律是1X2.2X3.3X4.4X5.5X6.6X7. 1x3＋2x4＋3x5＋…9x11 x1-x2+x3=1x2-x3+x4=21若x1,x2,x3,x4,x5满足方程组 x3-x4+x5=3x4-x5+x1=4x5-x1+x2=5求x2 x3 x4的值2已知 x1+x4+x6+x7=39 x2+x4+x5+x7=49 x3+x5+x6+x7=41 x4+x7=13 x5+x7=14 x6+x7=9 x1+x2+x3+x4+x5+x6+x7=9求x7的值若x1,x2,x3,x4,x5满足方程组 x1-x 1/1x3+1/2x4+1/3x5+1/4x6+...+1/100x102=? 1x3+2x4+3x5+4x6..+99x101=? 1x2+2x3+3x4+4x5+5x6---+99x100=? 1x2+2x3+3x4+4x5+5x6+.+99x100 巧算：1x2+2x3+3x4+4x5+5x6+6x7...+8x9 X1＋X2＋X3＋X4＋X5＋X6＋X7＝2010,X1＋X2＝X3,X2＋X3＝X4,X3＋X4＝X5,X4＋X5＝X6,X5＋X6＝X7求X3最大值 1x2+2x3+3x4+4x5+5x6+6x7+7x8+8x9+9x10+10x11 1/1x2＋1/2x3＋1/3x4＋1/4x5＋1/5x6＋1/6x7＋1/7x8＋1/8x9＝?急! 1x2÷1＋2x3÷1＋3x4÷1＋4x5÷1＋5x6÷1.＋n(n＋1）÷1 1 1 1 1 1 ——＋——＋——＋——＋```````` —— 2X3 3X4 4X5 5X6 99X100