Merge pull request #26 from linebender/sqrt

Quadratic formula: Sorry it was paining me too much.

content/wiki/_index.md

@@ -6,7 +6,7 @@ Changes to this Wiki are welcome; send a pull request to the [linebender.github.
 detailed review.
 
 Note that math is supported between two dollar signs `$$` thanks to [MathJax]. 
-For example, `$$x = \frac{-b \pm \( b^2 - 4ac\)}{2a}$$` outputs $$x = \frac{-b \pm \( b^2 - 4ac\)}{2a}$$
+For example, `$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$` outputs $$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
 
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