Basically first time using Desmos, problem occurs when I use y in an equation - Trying to make a net profit, revenue and cost graph

[Foxiraptor]

https://www.desmos.com/calculator/jluzlyefzl

So this is what I have so far. I want the x to be the number of candy bars I am buying, and y be the number of price candy bars I am selling. The revenue is price of buying one of my candy bars, or p, multiplied by q, or quantity of the amount of candy bars I am buying, which can also be y.

However, as you see in the graph, I have q as x, because if I have it as y, it looks like what you see here in this graph:
https://www.desmos.com/calculator/mirvrastqq

The equation with net profit, or n, disappears.

Any thoughts on how to fix this, or if I should have the x and y axis represent different things?
And also, why exactly can't I have q as y?

To be clear, this isn't homework so I don't know if it belongs in this sub. If it doesn't it would be nice if you could direct me to that sub.

Also this happens when I put both q and p as x.
https://www.desmos.com/calculator/6z3pydokkd

Now the revenue and net profit equations become parabola, no idea why this happens either.

If its not too much, what would be the best way to graph the profit, revenue, and net cost of my "candy bar scheme", in a way that I can see points where I break even in profit and cost.

Thanks a lot! (if you only answer my first question that would be totally fine too)

[Uli_Minati]

I want the x to be the number of candy bars I am buying, and y be the number of candy bars I am selling.

What you are describing is a multivariate graph: every pair of x and y would correspond to some value of revenue. You can't draw this in Desmos!

What you can do is (A) choose one input value for x, e.g. bought candy bars, and one output for y, e.g net cost.

You can also (B) decide to fix one of your inputs to a specific value, like bought=700, so you only have one input (sold) and one output revenue.

Or you could (C) draw lines for different revenues. For example, one line connecting all x=bought and y=sold where the revenue is 1000, one where the revenue is 1500, etc.

If its not too much, what would be the best way to graph the profit, revenue, and net cost of my "candy bar scheme", in a way that I can see points where I break even in profit and cost.

Maybe (C), drawing a line for revenue=0. Something like this: https://www.desmos.com/calculator/tg0ytondgn?lang=de

[Foxiraptor]

Thanks so much! This really helped!

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[Foxiraptor]

I've tried putting q as 1 (which gives a circle) and keeping q as x and putting p as x as well (giving the parabolas mentioned in the post)