ELI5: Explain Like I'm 5

Linear Diophantine equation

A linear diophantine equation is a really big math problem that involves finding some special numbers that work together. Imagine you have some stickers and you want to use them to decorate a really big wall. You know that you need to put the stickers in a certain pattern, like in rows and columns, to make it look pretty. But you have a problem: you only have a few stickers, and you need to figure out how many rows and columns you can make with them.

That's what a linear diophantine equation is like. It's a big math problem that tries to figure out how many rows and columns you can make with a certain number of stickers. But instead of stickers, we use numbers called "coefficients" to represent how many rows and columns we can make. And instead of a wall, we use a math formula that tells us how those numbers have to work together.

The formula for a linear diophantine equation looks like this:

ax + by = c

Here, "a", "b", and "c" are all special numbers that we know, and "x" and "y" are the ones we're trying to figure out. The formula says that if we multiply "a" by "x" and "b" by "y" and add them together, we should get the number "c".

Now, that might sound easy, but it's actually really hard to figure out what "x" and "y" should be. It's like trying to solve a really hard puzzle. But mathematicians have figured out some tricks to make it easier. They use something called "Euclidean division" to break the problem down into smaller parts, and they use something called the "extended Euclidean algorithm" to find the solutions.

The extended Euclidean algorithm is like a really fancy math tool that helps us figure out what "x" and "y" should be. It uses something called "gcd", which stands for "greatest common divisor", to help us find the solutions. Basically, we keep dividing the numbers "a" and "b" by their gcd until we find two special numbers that work together to make the solution.

It's kind of like if we have a big cake and we want to divide it up into smaller pieces. We use a knife to cut the cake into smaller slices, and we keep doing that until we get the right number of slices for everyone to have a piece.

So, in the end, a linear diophantine equation is just a big math problem that helps us figure out how to divide things up evenly using special numbers. It might sound complicated, but it's actually kind of like solving a puzzle or dividing up a cake!