Question 340307:  If n and p are different positive prime numbers, which of the integers n^4, p^3 and np has (have) exactly 4 positive divisors?
 
(A) n^4 only 
(B) p^3 only 
(C) np only 
(D) n^4 and np 
(E) p^3 and np
 
 
Could you please explain the above problem. 
 Answer by AnlytcPhil(1810)      (Show Source): 
You can  put this solution on YOUR website! If n and p are different positive prime numbers, which of the integers n^4, p^3 and np has (have) exactly 4 positive divisors? 
 
n4 = nnnn has divisiors 1,n,nn,nnn,nnnn that's 5 
p3 = ppp has divisors 1,p,pp,ppp, that's 4 
np has divisors 1,n,p,np, that's 4
 
So the answer is
 
(E) p3 and np
 
Edwin  
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