1. Press Shift and click the green flag to turn on Turbo Mode (otherwise it would take forever to draw the function). 2. Go inside the project and click the button located in the top right that says "Remix". 3. Change what y is set to (but keep x position somewhere in the function).
For a very smart graphing calculator go to desmos.com. That website can graph way more than just a function. Note that the current formula is x=y.
