LaTeX subscript notation doesn't work and every other way I could think of making something subscripted didn't work. Why hasn't this been added?
Have you tried the Subscript and Superscript functions? There's also the Basic Math Assistant under the Palettes menu item so one can point and click one's way to special formatting.
But you'll find that making equations "pretty" don't always work like you think they should. You might be better off using constructs like x, x, etc. (not to be confused with "Part" which uses double square brackets: [[...]]).
If you try these for yourself you will see that they do not work. There seems to be no way to make a lowered index.
Have you tried
If there's something you've tried and found it "doesn't work", please give a specific example.
Sorry, I'm an idiot. I foolishly did not notice the "Wolfram|Alpha" and assumed this was about Mathematica. I know nothing about Wolfram|Alpha.
There is a way. Look at the Notations` package