deletions | additions       diff --git a/untitled.tex b/untitled.tex  index d5b14ce..645c2bc 100644  --- a/untitled.tex  +++ b/untitled.tex 
...
$\Leftrightarrow x^2 +y^2 + cx-dy + b=0$\\  $\Leftrightarrow (x^2+cx) +(y^2-dy) +b =0$\\  $\Leftrightarrow (x+\frac{1}{2}c)^2 + (y-\frac{1}{2}d)^2 = -b + \frac{1}{4}(c^2+d^2)$ by completing the square\\  The equation above is a circle with a radius of $\sqrt{-b + \frac{1}{4}(c^2+d^2)$ \frac{1}{4}(c^2+d^2)}$