An integer has to be either even or odd
Even numbers are numbers divisible by 2, while odd numbers are not
Let us represent the 2 even numbers like this
ax+1
bx+1
When you add the two numbers together, you get
2a + 1 + 2b + 1
This can be simplified using the inverse of distributive property
2(a+b) + 2
2(a+b+1)
This is the sum, which is divisible by 2
