计算1x2x3+2x3x4+…+48x49x50
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计算1x2x3+2x3x4+…+48x49x50
原式=2*(2²-1)+3*(3²-1)+……+49*(49²-1)
=(2³+3³+……+49³)-(2+3+……+49)
=(1+2+3+……+49)²-(1+2+3+……+49)
=1225³-1225
=1838265625-1225
=1838264400
=(2³+3³+……+49³)-(2+3+……+49)
=(1+2+3+……+49)²-(1+2+3+……+49)
=1225³-1225
=1838265625-1225
=1838264400
计算1\1x2x3+1\2x3x4+1\3x4x5+``````+1\48x49x50注:(\)为分数线(x)为乘号
1/1x2x3+1/2x3x4+1/3x4x5+1/4x5x6+.+1/48x49x50=
1/2x3x4+1/3x4x5+1/4x5x6+……+1/48x49x50=
1x2X3+2x3X4+3x4X5+…+7X8X9=?
1x2x3+2x3x4+3x4x5+…+8x9x10
数学简便计算1/1x2x3+1/2x3x4+1/3x4x5……+1/20x21x22=?
1x2x3+2x3x4+3x4x5……+10x11x12巧算 请在两天之内回答
1/1x2x3+1/2x3x4+1/3x4x5
求和1x2x3+2x3x4+...+n(n+1)(n+2)
1x2x3+2x3x4+3x4x5+...+7x8x9=,
1x2x3+2x3x4+3x4x5+.+10x11x12
急,裂项法计算1.1/1x2x3+1/2x3x4+…+1/n(n+1)(n+2)2.2/(X+2)(X+4)+2/(X+