Multiple choice

If n is a positive integer, which of the following must be an odd integer?

  1. n + 3

  2. 3n2 + 1

  3. 5n + 3

  4. n2 + 2n

  5. n2 + n + 1
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

We should try one odd value (say, 1) and one even value (say 2) for n for each of the choices. Let us start with choice (5). lf n = 1, (5) = 1+ 1 + 1 = 3. If n = 2, (5) = 4 + 2 + 1 = 7. Both are odd numbers. So, we can stop here and choose (5) itself as the answer. (You can independently verify why  the other choices are wrong.).

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