1/2x5+1/5x8+1/8x11+…………+1/2003x2006+1/2006x2009 = 这是我儿子的小学作业

来源：学生作业帮编辑：作业帮分类：数学作业时间：2024/05/13 23:31:49

1/2x5+1/5x8+1/8x11+…………+1/2003x2006+1/2006x2009 = 这是我儿子的小学作业,我想不出简便算法……

1/2x5+1/5x8+1/8x11+…………+1/2003x2006+1/2006x2009
=1/3x(3/2x5+3/5x8+.+3/2006x2009)
=1/3x(1/2-1/5+1/5-1/8+...+1/2006-1/2009)
=1/3x(1/2-1/2009)
=1/3x2007/2009
=669/2009

1/2x5+1/5x8+1/8x11+…………+1/2003x2006+1/2006x2009 = 这是我儿子的小学作业 2x5/1+5x8/1+8x11/1+.2006x2009/1+2009x2012/1 用裂项法计算裂项法1/2X5+1/5x8+1/8x11.1/2009x2012=? 1/2x5+1/5x8+1/8x11+.+1/32x35 求前n项和1.1/(2X5),1/(5X8),1/(8X11)...2.2＾2/(1X3),4＾2/(3X5),6＾2/ 求数列1/2x5,1/5x8,1/8x11...,1/(3n-1)(3n+2)...的前n项和 1x5+2x5+3x5+4x5+5x5… 麻烦给我一个公式. 2x2/1x3+4x4/3x5+6x6/5x7+8x8/7x9+10x10/9x11+12x12/11x13 仔细看看 1x2+2x3+3x4+4x5+……+10x11 因式分解:X15+X14+X13+X12+X11+X10+X9+X8+X7+X6+X5+X4+X3+X2+X+1 1/1x2+1/2x3+1/3x4+1/4x5+```````+1/2008x2009=? 2/1x3+2/3X5+2/5x7=2/7x9+2/9x11