TeX Quellcode:

{-72a^2+36ac-\dfrac{9}{2}c^2 = -\dfrac{1}{2}\left(144a^2-72ac+9c^2\right) = -\dfrac{1}{2}\left(12^2a^2-2\cdot 12\cdot 3ac+3^2c^2\right) = -\dfrac{1}{2}\left(12a-3c\right)^2}