# Math Help - If x and y are both odd numbers, which of the following numbers must be an even numb

1. ## If x and y are both odd numbers, which of the following numbers must be an even numb

 If x and y are both odd numbers, which of the following numbers must be an even number?
xy
xy + 2
x + y
2x + y
x + y + 1
None of the above
I don't know

2. ## Re: If x and y are both odd numbers, which of the following numbers must be an even n

Try an example. In this particular problem, one example is sufficient because for each expression f(x,y) (i.e., f(x,y) = xy, f(x,y) = xy + 2, etc.), f(x,y) is either always even or always odd under the assumption that x and y are odd.

However, you should also be able to prove the correct answer. Since x is odd, x can be represented as 2x' + 1 for some integer x'. For example, 7 = 2 * 3 + 1 and -7 = 2 * (-4) + 1. Similarly, y = 2y' + 1 for some integer y'. What do you get when you multiply x and y and simplify the result?

3. ## Re: If x and y are both odd numbers, which of the following numbers must be an even n

Any odd number can be written in the form 2n+1 where n is a an integer so let first number=2m+1 2nd number =2n+1 and you will be able to answer the questions.