An easy functional equation

I obtained a pen tablet recently and am testing it out.

In this video, I talk about functional equations. A functional equation is similar to a "regular" equation, except that the quantity that we're solving for is an entire function, and not just a single numerical value. We can apply some of the rules of algebra and calculus (in this case, it's just algebra) to solve functional equations. In our example, we can swap variables and use standard algebraic techniques to solve four the answer and check it.

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That functional equation has NO valid solutions since if you apply (x, y)=(-1, -1), you will get 1=0, which is a contradiction.