Direct Proof - Example

Example

What follows is a simple, direct proof that the sum of two even integers is itself an even number.

Consider two even integers x and y. Since they are even, they can be written as x=2a and y=2b respectively for integers a and b. Then the sum . From this it is clear x+y has 2 as a factor and therefore is even, so the sum of any two even integers is even.

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