+3453 $$\begin{array}{l}
\left(-\frac{5}{6}\right) + \left(-\frac{8}{9}\right)\\
The\;problem\;here\;is\;that\;we\;need\;a\;common\;denominator.\\
To\;fix\;this,\;let's\;multiply\;the\;first\;fraction\;by\;\frac{3}{3}\;
and\;the\;second\;fraction\;by\;\frac{2}{2}.\\
This\;will\;give\;us\;a\;common\;demoninator\;(bottom\;number)\;of\;18.\\
\left(\frac{-5}{6}\times\frac{3}{3}\right) + \left(\frac{-8}{9}\times\frac{2}{2}\right)\\
\left(\frac{-15}{18}\right) + \left(\frac{-16}{18}\right)\\
Now\;that\;we\;have\;a\;common\;demoninator,\;we\;can\;add\;these\;fractions.\\
\left(\frac{-31}{18}\right)\\
So,\;that's\;our\;answer.\;You\;could\;also\;write\;this\;as\;a\;mixed\;number\;like\;so:\\
-1\frac{13}{18}\\
\end{array}$$
+3453 $$\begin{array}{l}
\left(-\frac{5}{6}\right) + \left(-\frac{8}{9}\right)\\
The\;problem\;here\;is\;that\;we\;need\;a\;common\;denominator.\\
To\;fix\;this,\;let's\;multiply\;the\;first\;fraction\;by\;\frac{3}{3}\;
and\;the\;second\;fraction\;by\;\frac{2}{2}.\\
This\;will\;give\;us\;a\;common\;demoninator\;(bottom\;number)\;of\;18.\\
\left(\frac{-5}{6}\times\frac{3}{3}\right) + \left(\frac{-8}{9}\times\frac{2}{2}\right)\\
\left(\frac{-15}{18}\right) + \left(\frac{-16}{18}\right)\\
Now\;that\;we\;have\;a\;common\;demoninator,\;we\;can\;add\;these\;fractions.\\
\left(\frac{-31}{18}\right)\\
So,\;that's\;our\;answer.\;You\;could\;also\;write\;this\;as\;a\;mixed\;number\;like\;so:\\
-1\frac{13}{18}\\
\end{array}$$
+118608 Hi Ninja,
Another way to write words is with a message box \mbox{This will be a comment}
I saw heurika use some other command for a message but this is the one i use.
You cannot put any maths things inside the parenthenses LaTex will not accept it.
+3453 Thanks Melody.
I see Alan did a similar thing..but it looks like he did two dolar signs? I'm not sure, here's his post on this: http://web2.0calc.com/questions/find-the-average-slope#r5
+118608 Alan is here so he can tell us! Please Alan.
I actually don't think that Alan's $ signs did anything.
If you are working with LaTex away from a forum you need to put $ signs around the maths made parts.
On forums this is effectively done for you. I know Alan writes a lot of his Latex and coppies it over. He probably didn't here but the $ signs would just be a habit that he is in.
I don't know why he has put the 2 extra dollar signs at the front. I think he would b e happy to tell us though.
This was your code Alan
$$$\int dx$
$$$\int dx$$$
-------------------------------------------------------------------
The other day Heureka used something else instead of \mbox{}
It had the same purpose. I cant remember what it was but it would be referred to in the LaTex thread for sure. I have been faily consciencious about updating and adding to the LaTex thread. Although I will admit that it is a bit of a mess. 
+33615 NinjaDevo sent me a message about this. Here's a copy of the reply I sent him:
The default for the LaTeX box on the site is to be in "Display" math mode. I often switch this off to begin with by inserting $$ right at the start. If I then type words it comes out as text.
In the "average slope" case I wanted to start with some "Inline" math, which requires a single $ immediately before and immediately after the math (so it looks like I started the whole thing with 3 dollar signs - 2 to switch off the default "Display" mode and 1 to switch on the "Inline" mode).
Putting $$ immediately before and after the math produces "Display" mode math, where the math appears centred on a new line.
You switch off math mode and enter text mode by using either $ (for "Inline" math) or $$ (for "Display" math).
Hope this helps.
PS I'm no LaTeX expert - I just use trial and error and see what results!
