Multiple choice general knowledge math & puzzles

If a and b are both even numbers, which of the following could be and odd integer?

  1. a2 + b2

  2. (a + 1)^2 + (b + 1)^2

  3. (a + 1)*(b + 1) - 1

  4. (a + 1) / (b + 1)
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

If $a, b$ are even, $a+1$ and $b+1$ are both odd. The ratio of two odd numbers can be an integer (e.g., $9/3 = 3$), and that integer will always be odd. The other options result in even numbers: (odd+odd=even), (odd*odd-1=even).

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