100737

P and Q represent different positive integers.  Find all values of both P and Q such that the product of the product of P and Q and the difference of P less Q is equal to 100737.  In other words, PQ\left ( P-Q \right )=100737.
Source: mathcontest.olemiss.edu 10/11/2010

Solution
First, let’s write the prime factorization of 100737=3\cdot3\cdot3\cdot7\cdot13\cdot41.
The problem asks us to rewrite 100737 as a product of three factors, i.e. 100737=\left ( P \right )\left ( Q \right )\left ( P-Q \right ).
Example 1: 100737=\left ( 39 \right )\left ( 41 \right )\left ( 63 \right )
Example 2: 100737=\left ( 3 \right )\left ( 123 \right )\left ( 273 \right )
In Example 1, if we let P=63 and Q=41, then P-Q=63-41=22\neq 39, so this is not a solution.
In Example 2, if we let P=273 and Q=123, then P-Q=273-123=150\neq 3, so this is not a solution.

Notice that the factors are always odd, because there is no 2 in the prime factorization of 100737.
In Example 1, 39=3\cdot13 and 63=3\cdot21. In Example 2, 123=3\cdot41 and 273=3\cdot7\cdot13.

Thus, the third factor \left ( P-Q \right ) must be odd, but this is not possible because when you subtract two odd numbers you always get an even number.

We conclude that there are no different positive integers P and Q such that PQ\left ( P-Q \right )=100737.
We can check our answer by looking at the list of all possible groups of three factors below:

3

3

11193

100737

3

7

4797

100737

3

9

3731

100737

3

13

2583

100737

3

21

1599

100737

3

39

861

100737

3

41

819

100737

3

63

533

100737

3

91

369

100737

3

117

287

100737

3

123

273

100737

7

9

1599

100737

7

39

369

100737

7

117

123

100737

9

13

861

100737

9

21

533

100737

9

39

287

100737

9

41

273

100737

9

91

123

100737

13

21

369

100737

13

63

123

100737

21

39

123

100737

21

41

117

100737

39

41

63

100737

About mvtrinh

Retired high school math teacher.
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