If n is a positive integer and p is an odd prime , then find the number of pairs ( n , p ) of the equation n 3 + n 2 + n + 1 = p 6 .
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LHS is okk but why RHS will always have other than 0,2,6 as last digit ?
Rewrite the equation as ( n + 1 ) ( n 2 + 1 ) = p 6 Note that both of the factors on the LHS are greater than 1. Also, observe that the only prime divisor of both of the factors of LHS is p . It means that p ∣ n + 1 and p ∣ n 2 + 1 . So p ∣ n ( n + 1 ) − ( n 2 + 1 ) = n − 1 and p ∣ n + 1 − ( n − 1 ) = 2 Therefore p = 2 and ( n + 1 ) ( n 2 + 1 ) = 6 4 It is clear that n < 5 , but none of the possibilities work. No solution.
Nice solution.Thanks
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n^3+n^2+n+1 = p^6
n^3+n^2+n = p^6 - 1
n^2 x (n+1) = (p^3+1) (p^3-1)
Notice: From the LHS, if we input some values of n, we always obtain products having the last digit (Either 0, 2 or 6)
From the RHS, however, when we input some values of p, where p is odd prime, we always obtain digits other than (0, 2 or 6)
Hence, there is no solution.