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A problem on factors (Posted on 2007-07-16) Difficulty: 3 of 5
Let P(X,A) be the number of positive divisors of A not greater than X; for example, P(1,12)=1, P(2,12)=2, and P(12,12)=6.

1)If P(12,A)=7 and P(A,A)=10, what's A?
2)If x*y is a divisor of A, then show that P(x*y,A) ≥ P(x,A)+P(y,A)-1

See The Solution Submitted by Praneeth    
Rating: 4.0000 (1 votes)

Comments: ( Back to comment list | You must be logged in to post comments.)
re: Part 1 Comment 2 of 2 |
(In reply to Part 1 by Jer)

Its obviously true,if x and y are primes and x*y=A.
You have taken that case only and that too 4=2+3-1.

Edited on July 17, 2007, 5:51 am
  Posted by Praneeth Yalavarthi on 2007-07-16 12:11:36

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