Are they both perfect cubes?

Find the sum of all ordered pairs of positive integers ( m , n ) (m,n) such that both 3 m + n 3m+n and 3 m 2 + n 2 3m^2+n^2 are perfect cubes.

If none such pair exists then enter 0.


The answer is 0.

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1 solution

Cantdo Math
Apr 18, 2020

Assume the contrary.Let, 3 m + n = a 3 3m+n=a^3 and 3 m 2 + n 2 = b 3 3m^2+n^2=b^3 . Multiplying them and some algebra gives, ( 2 m ) 3 + ( m + n ) 3 = ( a b ) 3 (2m)^3+(m+n)^3=(ab)^3 which contradicts the fermat's last theorem. Hence,no such pair exist and the answer is 0.

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