If are the integers, whose sum of any two variables is larger than 1, that satisfy the system above, what is the value of ?
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( a + b + c ) 3 = a 3 + b 3 + c 3 + ( 3 a b 2 + 3 a c 2 + 3 b a 2 + 3 b c 2 + 3 c a 2 + 3 c b 2 + 6 a b c )
( a + b + c ) 3 − ( a 3 + b 3 + c 3 ) = 3 ( a b 2 + a c 2 + b a 2 + b c 2 + c a 2 + c b 2 + 2 a b c ) = 3 ( a + b ) ( b + c ) ( c + a )
From the system above, ( a + b + c ) 3 − ( a 3 + b 3 + c 3 ) = 1 1 3 − 7 8 5 = 5 4 6 = 3 ( a + b ) ( b + c ) ( c + a )
Hence, ( a + b ) ( b + c ) ( c + a ) = 1 8 2 = 2 × 7 × 1 3 .
Since a , b , c are integers, each sum of the two variables will equal to each of the three primes presented. Covering the cyclic solutions, we can set up the new system of equations as followed:
a + b = 2 b + c = 7 c + a = 1 3
Then c − a = 5 , and 2 c = 1 8 ; c = 9 .
Hence, a = 4 , and b = − 2 .
Thus, a 2 + b 2 + c 2 = 4 2 + ( − 2 ) 2 + 9 2 = 1 0 1 .