大师作文网1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(20x21x22)=?
来源：学生作业帮 编辑：大师作文网作业帮 分类：数学作业 时间：2024/11/20 11:03:05
1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(20x21x22)=?
1/(1*2*3)+1/(2*3*4)+1/(3*4*5)+.1/(20*21*22)
=1/2[1/1*2-1/2*3]+1/2[1/2*3-1/3*4]+1/2[1/3*4-1/4*5]+...+1/2[1/20*21-1/21*22]
=1/2[1/1*2-1/2*3+1/2*3-1/3*4+1/3*4-1/4*5+...+1/20*21-1/21*22]
=1/2[1/2-1/21*22]
=1/2*115/231
=115/462
=1/2[1/1*2-1/2*3]+1/2[1/2*3-1/3*4]+1/2[1/3*4-1/4*5]+...+1/2[1/20*21-1/21*22]
=1/2[1/1*2-1/2*3+1/2*3-1/3*4+1/3*4-1/4*5+...+1/20*21-1/21*22]
=1/2[1/2-1/21*22]
=1/2*115/231
=115/462
1/(1x2x3)+1/(2x3x4)+1/(3x4x5)+.1/(20x21x22)=?
数学简便计算1/1x2x3+1/2x3x4+1/3x4x5……+1/20x21x22=?
1/1x2x3与1/2x3x4、1/3x4x5、依此类推以至于1/20x21x22的总和是多少?
1x2X3+2x3X4+3x4X5+…+7X8X9=?
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1/1x2x3+1/2x3x4+1/3x4x5
1x2x3+2x3x4+3x4x5+…+8x9x10
1x2x3+2x3x4+3x4x5+.+10x11x12
1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+.+1/48x49x50=
1/1x2x3+1/2x3x4+1/3x4x5+.+1/11x12x13=
1/1x2x3+1/2x3x4+1/3x4x5+.+1/9x10x11=
请1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6=