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Integers involved in factors (Posted on 2019-05-17) Difficulty: 2 of 5
xy = 22 * 34 * 57 * (x + y)

If x and y satisfy the above condition, then find the number of positive integral solutions.

No Solution Yet Submitted by Danish Ahmed Khan    
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solution | Comment 1 of 2
For convenience in typing, call the numeric portion of RHS 'A'.

xy-Ax-Ay=0 and (x-A)(y-A)=A^2

Let k = the amount x differs from A so that x=A+k.

Then (A+k)*y=A*(A+k+y) and y=(A^2)/k + A.

So every factor of A^2 gives a solution.  Since A^2 = 2^4*3^8*5^14 there are 5*9*15 = 675 factors.  But x and y can be swapped which adds a factor of 2.  In addition, x=y=2A is double counted so the number of solutions is 2*675-1=1349.

  Posted by xdog on 2019-05-18 19:39:16
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