Find the minimum value of for which the expression is rational.
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Let's say that n − 1 + n + 2 0 1 4 = x n is rational for some n. So, 1 / x n should also be rational. ⇒ 2 0 1 5 n + 2 0 1 4 − n − 1 is also rational. Therefore, n + 2 0 1 4 − n − 1 is also rational. As the sum of two rationals cannot be irrational, we find out that n − 1 and n + 2 0 1 4 are rational. As n ϵ N , let for some x , y ϵ N , n + 2 0 1 4 = x 2 a n d n − 1 = y 2 . ⇒ x 2 − y 2 = ( x − y ) ( x + y ) = 2 0 1 5 = 5 × 1 3 × 3 1 . 2015 has only 8 factors. This means that x+y=65, 155, 403, 2015.and x-y=31, 13, 5, 1. Solving these equations, we can get that minimum value of y=17. ∴ n = 2 8 9 + 1 = 2 9 0