Find the total number of pairs of positive integer primes such that .
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I Really do not understand which primes satisfy the condition.
If p = 2 , then 3 . 2 q − 1 + 1 ∣ 1 1 2 + 7 2 = 1 7 0 . Therefore q ≤ 6 and for non of such q the condition is satisfied.
If p = 2 , then p is odd and 1 1 p + 7 p = ( 1 1 + 7 ) ( 1 1 p − 1 − 1 1 p − 2 . 7 + 1 1 p − 3 . 7 − ⋯ + 7 p − 1 ) . So, 4 ∤ 1 1 p + 7 p . But, if q is odd then 4 ∣ 3 . p q − 1 + 1 , because (knowing Euler theorem)
3 . p q − 1 ≡ − 1 . ( p 2 ) k ≡ − 1 m o d 4
So, for no prime pair ( p , q ) the condition is satisfied.