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Algebra Difficulty 1.4 Junior Find the answer

Which of the following expressions is equal to an odd integer for every integer nn?

A number or a short expression. Spacing and $ signs are ignored.

Solution

When n=1n=1, the values of the five expressions are 2014, 2018, 2017, 2018, 2019.
When n=2n=2, the values of the five expressions are 2011, 2019, 4034, 2021, 2021.
Only the fifth expression (2017+2n)(2017+2n) is odd for both of these choices of nn, so this must be the correct answer.
We note further that since 2017 is an odd integer and 2n2n is always an even integer, then 2017+2n2017+2n is always an odd integer, as required.

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