Problems need HardWork #9

How many integer value of n n are there such that n 1450 n \dfrac n{1450 - n} is a perfect square?

infinite 7 13 0

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3 solutions

Here let 1450 be 2 5 5 29 by factorizIng. Then, let the question be converted as n/(1450-n)=y^2 Or, n(1+y^2)=2 5^2 29 y^2 Here, y^2+1 can only be divisible by 2,5^2,29 and its combinations.. but not by y^2. Now, when y={0,1,2,3,7,12,17}, y^2+1 has the prime factors only of 2,5,29. And we will check for all combination possible that is 12, but for 7 values it satisfy the condition above. Therefore, there are 7 values of y is possible . Thus, 7 values for n is possible only.

Is 0 also a perfect square? I think 6 possible values is a better answer.

Anshuman Singh Bais - 5 years, 9 months ago
Edwin Gray
Feb 21, 2019

The values of n are: 0,725, 1160, 1305, 1421, 1440, 1445, The squares are 0, 1, 2, 3, 7, 12, 17.

Aditya Kumar
Jun 9, 2016

Just rewrite the expression as 1/((1450/n)-1) , and then check factors of 1450

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