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1. what is the volume of a certain rectangular solid?
1) two adjacent faces of the solid have areas 15 and 24, respectively,
2) Each of two opposite faces of the solid has area 40.
从1)中, 可看出至少这两个面有一个公因子, 因为相邻面,那公边就只能是3, 其它两条边为5,8-------->能推出体积. 我选了A, 答案确是C. 不明白.
2. is ab=1?
1) aba=a
2) bab=b
我选了D, 两边同时约A 或B. 答案是E, 为什么?
3. 直线 aX +b Y+C=0, 怎么求斜率? 公式是怎样?多谢 | 
