Prove that the product of an odd number with an even number is an even number.
Prove that the square of any even number is a multiple of the number 4.
A even number will have a factor of 2, and any number with 2 as a factor will be even.
So if your multiply a number with another number that has the factor 2, it'll also have the factor 2, making it even.
So if a even number has the factor 2, then if it's squared it has the factor 2^2 = 4, meaning that it's a multiple of 4.
I hope this helped. :)))