The reason that this is doing that is because
is the same thing as
Well, you can't quite get exactly what you want. This is because the 83 series doesn't support symbolic expressions; stuff like this would be simple on an 89 or an Nspire. There are 3 ways to get stuff on the home screen (that i know of), each have their advantages and disadvantages.
This one is the only one that lets you give more than one argument at a time, although doing so makes no difference from seperating it out. What makes Disp unique is that it follows the rules as though you had punched it into the home screen outside of a program. When you try to display something that is longer than one line, it replaces the last character with an ellipsis (…). You can't scroll to see the rest.
Yes, you can give pause an extra argument and it will display it to the home screen. The main reason that you would use this is because if you try to display something larger than will fit on one line, it will replace the last character with "…", but it will also let you scroll to see the rest of it, unlike. Like Disp, it follows the rules as though you had punched it into the home screen outside of a program; but unlike Disp, it treats stuff that was put on the screen by output as thought it had been put there by disp.
Unlike the other 2, output doesn't work on a line basis, it goes off of home screen coordinates. This can be an issue when you have numbers that could be either 1 or 2 digits. If you try to display something that would go off the screen, it just wraps around to the next line.
To make it the exact way that you want it in your scenario, well I not sure how to do it. Here's what I'd do.
This would display it on the screen like when you do a regression- equation at top, with variables written underneath. I'm thinking that even the TIOS has it this way because their operating system doesn't support symbolic expressions, and this still looks neat.
EDIT: I added info for when displaying stuff longer than a line.