Functions of Several Variables

So far every function had a single input: feed it x, get back f(x). But the real world rarely depends on just one thing. The temperature in a room depends on where you are — left/right AND front/back. The cost of a trip depends on distance AND fuel price. To model that, we let a function take two inputs at once: f(x, y). Same idea as before — a machine that turns inputs into one output — but now there are two knobs to turn.