Corrected typo in the basics of PE page, maths section. The parenthesis...

Corrected typo in the basics of PE page, maths section. The parenthesis containing the squared exponent should read (y_i - (t_i * m + c)) instead of (y_i - (t_i * x + c)) for a model H defined by y = m*x + c.

docs/basics-of-parameter-estimation.txt

@@ -41,7 +41,7 @@ Gaussian distributed as such:
 .. math::
 
    P(y_i, t_i| m, c, H) = \frac{1}{\sqrt{2\pi\sigma^2}}
-                         \mathrm{exp}\left(\frac{-(y_i - (t_i x + c))^2}{2\sigma^2}\right) \,.
+                         \mathrm{exp}\left(\frac{-(y_i - (t_i m + c))^2}{2\sigma^2}\right) \,.
 
 Next, we assume that all data points are independent. As such,