Show equation being plotted

[jeanimal]

Right below the degree text box, added a new textbox that is disabled (uneditedable) with the equation actually being plotted, based on the degree. For example
degree equation
1 a0 + x^1 = 0
2 a0 + a1 x^1 + x^2 = 0
3 a0 + a1 x^1 + a2 x^2 + x^3 = 0

I had the idea to add the equation because I was confused. The coefficient labels on the plot did not obviously match the equation at the top of the "Explanation" section-- e.g. for degree n there is no a_n-- so I thought there was a mistake.

[duetosymmetry]

Please take a look at this page on the MathJax docs to see how to programmatically ask MathJax to typeset an equation after load time. I suspect it's not possible to have typeset math inside of a textarea? In that case, I'm not sure what's the right UI approach to make it clear that the equation is an output that's linked to the degree input.

[jeanimal]

New pull request for Latex version.
#3