ELI5: Explain Like I'm 5

Polynomial long division

Okay kiddo, have you ever had to divide bigger numbers by smaller ones? It can be tricky, right? Well, polynomial long division is a bit like that, but with letters instead of numbers!

Let's say we have a big long number, like this: 1674. And we want to divide it by a smaller number, like 6. We can do that using long division, where we write down how many times 6 goes into 16, then multiply that by 6 and subtract it from 16 to get 10. Then we bring down the next number, 7, and repeat the process until we get our answer.

Now, imagine that instead of numbers, we have variables like x and y. And instead of dividing by just one variable, we have an entire equation with multiple variables like this: x^3 - 4x^2 + x - 7. That's a mouthful, huh?

To simplify this equation, we can use polynomial long division. It's like long division with numbers, but we use variables instead! We take the highest power of x in the equation, which is x^3, and divide it by the highest power of x in the divisor (the thing we're dividing by), which might be something like x - 2. So we write x^3 / (x - 2) = x^2, because x^2 times (x - 2) equals x^3.

Then we multiply x^2 by the divisor, which gives us x^3 - 2x^2. We subtract that from the original equation, x^3 - 4x^2 + x - 7, and get 2x^2 + x - 7. We then repeat the process with the next highest power of x, which is x^2, and keep going until we can't divide anymore.

So polynomial long division is just like long division with numbers, but with letters instead. We use it to simplify complicated equations and make them easier to solve. Pretty cool, huh?