True or False?
For all even positive integers , is always an integer.
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Using the binomial expansion, ( 3 + 2 ) n + ( 3 − 2 ) n = [ 3 n + ( n 1 ) 3 n − 1 2 + ( n 2 ) 3 n − 2 2 2 + ⋯ + 2 n ] + [ 3 n − ( n 1 ) 3 n − 1 2 + ( n 2 ) 3 n − 2 2 2 + ⋯ + 2 n ] = 2 [ 3 n + ( n 2 ) 3 n − 2 2 2 + ( n 4 ) 3 n − 4 2 4 + ⋯ + 2 n ] Since n is an even positive integer, we can write n = 2 a for some integer a : = 2 [ 3 2 a + ( n 2 ) 3 2 a − 2 2 2 + ( n 4 ) 3 2 a − 4 2 4 + ⋯ + 2 2 a ] = 2 [ 3 a + ( n 2 ) 3 a − 1 2 + ( n 4 ) 3 a − 2 2 2 + ⋯ + 2 a ] which is an integer. Therefore the statement is True .