Find the number of integer pairs ( m , n ) satisfying the equation
m 3 + 6 m 2 + 5 m = 2 7 n 3 + 9 n 2 + 9 n + 1
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The given equation is equivalent to 3 ( 2 ( 3 m + 1 ) + 2 m 2 + 2 m − 9 n 3 − 3 n 2 − 3 n ) = 1
However, if m , n are integers, then the left side is an integral multiple of 3 while the right side isn't. Therefore there are 0 integral solutions ( m , n )
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Similar to @Brian Moehring solution, we may take both sides, mod 3
m 3 − m ≡ 1 ( m o d 3 )
Also G C D ( m , 3 ) = 1 , for if m is a multiple of 3 , then the RHS of the main equation should be divisible by 3 , which is not possible.
Since G C D ( m , 3 ) = 1 , using Fermat little theorem,
m 3 − m ≡ 1 ( m o d 3 ) ⟹ m − m ≡ 0 ≡ 1 ( m o d 3 )
which is a contradiction to the existence of any solution to the equation.