Given equation of the surface of 2-order:
$$4 x^{2} + 4 x y + 4 x z + y^{2} + 2 y z + z^{2} + 2 x + y + z - 2 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x z + a_{22} y^{2} + 2 a_{23} y z + a_{33} z^{2} + 2 a_{14} x + 2 a_{24} y + 2 a_{34} z + a_{44} = 0$$
where
$$a_{11} = 4$$
$$a_{12} = 2$$
$$a_{13} = 2$$
$$a_{14} = 1$$
$$a_{22} = 1$$
$$a_{23} = 1$$
$$a_{24} = \frac{1}{2}$$
$$a_{33} = 1$$
$$a_{34} = \frac{1}{2}$$
$$a_{44} = -2$$
The invariants of the equation when converting coordinates are determinants:
$$I_{1} = a_{11} + a_{22} + a_{33}$$
|a11 a12| |a22 a23| |a11 a13|
I2 = | | + | | + | |
|a12 a22| |a23 a33| |a13 a33|
$$I_{3} = \left|\begin{matrix}a_{11} & a_{12} & a_{13}\\a_{12} & a_{22} & a_{23}\\a_{13} & a_{23} & a_{33}\end{matrix}\right|$$
$$I_{4} = \left|\begin{matrix}a_{11} & a_{12} & a_{13} & a_{14}\\a_{12} & a_{22} & a_{23} & a_{24}\\a_{13} & a_{23} & a_{33} & a_{34}\\a_{14} & a_{24} & a_{34} & a_{44}\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}a_{11} - \lambda & a_{12} & a_{13}\\a_{12} & a_{22} - \lambda & a_{23}\\a_{13} & a_{23} & a_{33} - \lambda\end{matrix}\right|$$
|a11 a14| |a22 a24| |a33 a34|
K2 = | | + | | + | |
|a14 a44| |a24 a44| |a34 a44|
|a11 a12 a14| |a22 a23 a24| |a11 a13 a14|
| | | | | |
K3 = |a12 a22 a24| + |a23 a33 a34| + |a13 a33 a34|
| | | | | |
|a14 a24 a44| |a24 a34 a44| |a14 a34 a44|
substitute coefficients
$$I_{1} = 6$$
|4 2| |1 1| |4 2|
I2 = | | + | | + | |
|2 1| |1 1| |2 1|
$$I_{3} = \left|\begin{matrix}4 & 2 & 2\\2 & 1 & 1\\2 & 1 & 1\end{matrix}\right|$$
$$I_{4} = \left|\begin{matrix}4 & 2 & 2 & 1\\2 & 1 & 1 & \frac{1}{2}\\2 & 1 & 1 & \frac{1}{2}\\1 & \frac{1}{2} & \frac{1}{2} & -2\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}- \lambda + 4 & 2 & 2\\2 & - \lambda + 1 & 1\\2 & 1 & - \lambda + 1\end{matrix}\right|$$
|4 1 | | 1 1/2| | 1 1/2|
K2 = | | + | | + | |
|1 -2| |1/2 -2 | |1/2 -2 |
|4 2 1 | | 1 1 1/2| |4 2 1 |
| | | | | |
K3 = |2 1 1/2| + | 1 1 1/2| + |2 1 1/2|
| | | | | |
|1 1/2 -2 | |1/2 1/2 -2 | |1 1/2 -2 |
$$I_{1} = 6$$
$$I_{2} = 0$$
$$I_{3} = 0$$
$$I_{4} = 0$$
$$I{\left(\lambda \right)} = - \lambda^{3} + 6 \lambda^{2}$$
$$K_{2} = - \frac{27}{2}$$
$$K_{3} = 0$$
Because
$$I_{2} = 0 \wedge I_{3} = 0 \wedge I_{4} = 0 \wedge K_{3} = 0 \wedge I_{1} \neq 0$$
then by type of surface:
you need to
then the canonical form of the equation will be
$$I_{1} \tilde x^{2} + \frac{K_{2}}{I_{1}} = 0$$
$$6 \tilde x^{2} - \frac{9}{4} = 0$$
$$\left(\tilde x + 0\right)^{2} = \frac{3}{8}$$
this equation is fora type two parallel planes
- reduced to canonical form