Was genau ist das Problem - wo hakt es?
\( q_{A}:=\left[\begin{array}{ll}x & y\end{array}\right] \cdot A \cdot\left[\begin{array}{l}x \\ y\end{array}\right]+a \cdot\left[\begin{array}{l}x \\ y\end{array}\right]+a_{0} \)
\(\small A \, := \, \left(\begin{array}{rrr}2&1&-1\\1&2&-1\\-1&-1&2\\\end{array}\right)\), a=(0,0,0), a0=1
===> EW={4,1,1}
Drehung mit z.B.
\(\small R \, := \, \left(\begin{array}{rrr}\frac{1}{\sqrt{3}}&-\frac{2}{2 \; \sqrt{2}}&-\frac{1}{\sqrt{6}}\\\frac{1}{\sqrt{3}}&0&\frac{2}{\sqrt{6}}\\-\frac{1}{\sqrt{3}}&-\frac{2}{2 \; \sqrt{2}}&\frac{1}{\sqrt{6}}\\\end{array}\right)\)
===>
D:=diag(4,1,1)
\(q_D: \, 4 \; x^{2} + y^{2} + z^{2} = 1\)
Elipsoid in Hauptachsenlage (Translation nicht notwendig)
Detailrechung siehe: https://www.geogebra.org/m/pempffkx