又是两道DS

joywzy

17. Is the positive integer n equal to the square of an integer?
(1) For every prime number p, if p is a divisor of n, then so is p2.
(2)  is an integer.
Ans: B
I choose D
What does "then so is p2." mean?

18. What is the volume of a certain cube?
(1) The sum of the areas of the faces of the cube is 54.
(2) The greatest possible distance between two points on the cube is  
Ans: D
I guess the answer maybe wrong.

tongxun

18、D。cube=》立方体
17、没看明白题目

joywzy

（1）总面积知道，又如何知道体积？
（2）如何得出体积？
能否详细讲解，我还是不明白。

17的关键在于then so is p2.是什么意思？

joywzy

谢谢tongxun!

17题是什么意思？

lisaislisa

17.(1) For every prime number p, if p is a divisor of n, then so is p2.
--------------------------
means if p is a divisor of n ,then p^2 is the divisor of n too
it is insufficient , since P^2 is the divisor of N doen't mean that N=P^2
but I can not understand 2) , which is an integer?
anything missed ?

^^

joywzy

17,(2)根号N是整数，对不起是我漏了
（1）N=5*3^2，就不能满足；或是N=3^2，可满足

谢谢你参加讨论！