TeX source:
\begin{array}{rclll}\mathbb{D} &=& \mathbb{R} \cr\cr a\cdot4^a-2\dfrac{1}{4^{-a}}+a^2\cdot 4^a &=& 0 \\a^2\cdot 4^a+a\cdot4^a-2\cdot 4^a &=& 0 &\vert & :4^a\\a^2+a-2 &=& 0 &\vert & \text{p-q-Formel}\\a_{1,2} &=& -\dfrac{1}{2}\pm\sqrt{\left(\dfrac{1}{2}\right)^2+2}\\a_{1,2} &=& -\dfrac{1}{2}\pm\sqrt{\dfrac{9}{4}}\\\\a_1 &=& -\dfrac{1}{2}+\dfrac{3}{2} = 1\\a_2 &=& -\dfrac{1}{2}-\dfrac{3}{2} = -2\end{array}