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用简便方法计算:1x2x3+2x3x4+4x5x6+...+24x25x26

题目详情
用简便方法计算:1x2x3+2x3x4+4x5x6+...+24x25x26
▼优质解答
答案和解析
1x2x3+2x3x4+4x5x6+...+24x25x26
=1/4(-0x1x2x3+1x2x3x4)+1/4(-1x2x3x4+2x3x4x5)+……+1/4(-23x25x25+24x25x26x27)
=1/4[-0x1x2x3x4+24x25x26x27
=24x25x26x27/4
=6x25x26x27
=2x3x25x2x13x27
=4x25x13x27
=100x13x27
=35100