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Prime Pairs satisfy Quintic = Cubic (Posted on 2024-02-17) Difficulty: 3 of 5
Given that each of p and q is a prime number:

Determine all possible pairs (p,q) that satisfy this equation:

        p(p4+p2+10q) = q(q2+3)

See The Solution Submitted by K Sengupta    
Rating: 5.0000 (1 votes)

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Some Thoughts Analytic solution with computer verification | Comment 2 of 7 |
[This "proof" is not correct, see above responses]
If q = 2, then RHS = 14 and there is no solution.
Therefore q is odd which means RHS is even.
Which means p is even.
(in fact RHS is even whether q is even or odd)
Which means p = 2

The equation becomes:
    2(16 + 4 + 10*q) = q(q^2+3)
    40 + 20*q = q^3+3q
    q^3 - 17q - 40 = 0
    (q - 5)(q^2 + 5q + 8) = 0
    q = 5
(p,q) = (2,5) is the only solution

[below here is correct]
To confirm, testing primes up to 100,000 finds only one solution.
When (p,q) = (2,5) then both expressions = 140

----------
primes = [p for p in range(100000) if isprime(p)]

for p in primes:
    for q in primes:
        if p*(p**4 + p**2 + 10*q) == q*(q**2 + 3):
            print(p,q)

Edited on February 18, 2024, 9:25 am
  Posted by Larry on 2024-02-17 18:34:10

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