If
4 1 0 0 9 + 2 0 1 7 + 4 1 0 0 9 − 2 0 1 7 = 4 a + b c ,
where a , b , c are positive integers such that c is not divisible by the square of any prime, then find the value of c − a .
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x = 4 1 0 0 9 + 2 0 1 7 + 4 1 0 0 9 − 2 0 1 7 = 4 2 k 2 + 1 + k + 4 2 k 2 + 1 − k = 4 2 k 2 + 2 k + 1 + 4 2 k 2 − 2 k + 1 = 4 2 ( k + 1 ) 2 + 4 2 ( k − 1 ) 2 = 4 2 k + 1 + 4 2 k − 1 = ( 4 2 k + 1 + 4 2 k − 1 ) 2 = 2 k + 1 + 2 k 2 − 1 + k − 1 = 2 2 k + 2 k 2 − 1 = 4 2 k + k 2 − 1 = 4 2 4 ( k + k 2 − 1 ) 2 = 4 2 4 k 2 + 2 k k 2 − 1 + k 2 − 1 = 4 4 k 2 − 2 + 4 k k 2 − 1 = 4 4 ( 2 0 1 7 ) − 2 + 4 2 0 1 7 ( 2 0 1 6 ) = 4 8 0 6 6 + 4 8 2 8 2 3 8 Let k = 2 0 1 7 Putting back k = 2 0 1 7
⟹ c − a = 2 8 2 3 8 − 8 0 6 6 = 2 0 1 7 2
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Let, m n We m 4 + n 4 ( m n ) 2 ( m 2 + n 2 ) 2 ⟹ ( m 2 + n 2 ) m n ( m + n ) 2 ( m + n ) Let, u v ( u + v ) 2 ( m + n ) On ⟹ c − a = 4 1 0 0 9 + 2 0 1 7 , = 4 1 0 0 9 − 2 0 1 7 need to find m + n = 2 0 1 8 = 1 0 0 8 = ( m 4 + n 4 + 2 ( m n ) 2 ) = 4 0 3 4 = 4 0 3 4 ( 1 ) = 1 0 0 8 ( 2 ) = ( m 2 + n 2 + 2 m n ) = ( 4 0 3 4 + 4 0 3 2 ) From ( 1 ) and ( 2 ) = ( 4 0 3 4 + 4 0 3 2 ) = 4 0 3 4 = 4 0 3 2 = 8 0 6 6 + 2 4 0 3 4 × 4 0 3 2 = 8 0 6 6 + 4 8 2 8 2 3 8 = ( u + v ) = 4 8 0 6 6 + 4 8 2 8 2 3 8 comparing, we get a = 8 0 6 6 , b = 4 8 , c = 2 8 2 3 8 = 2 8 2 3 8 − 8 0 6 6 = 2 0 1 7 2