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5乘6乘7分之1乘6乘7乘8分之1

来源:学生作业帮 编辑:拍题作业网作业帮 分类:综合作业 时间:2024/04/27 16:02:51
5乘6乘7分之1乘6乘7乘8分之1
解5×6×1/7×6×7×1/8
=5×6×6×7×1/7×1/8
=5×6×6×1/8
=5×3×3×1/2
=45/2.
再问: 偶,对不起少加了个小括号。 (5乘6乘7)分之1加上(6乘7乘8)分之1加上(7乘8乘9)分之1
再答: 解原式 =1/(5×6×7)+1/(6×7×8)+1/(7×8×9) =1/7×[1/(5×6)+1/(6×8)+1/(8×9)] =1/7×1/3×[1/(5×2)+1/(2×8)+1/(8×3)] =1/7×1/3×1/2×[1/(5)+1/(8)+1/(4×3)] =1/42×[24/(120)+15/(120)+10/(120)] =1/42×49/120 =1/6×7/120 =7/720