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9x^2-36y^2+4z^2-18x+72y+16z-47=0 canonical form

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          2             2      2                  
-47 - 36*y  - 18*x + 4*z  + 9*x  + 16*z + 72*y = 0
$$9 x^{2} - 18 x - 36 y^{2} + 72 y + 4 z^{2} + 16 z - 47 = 0$$
9*x^2 - 18*x - 36*y^2 + 72*y + 4*z^2 + 16*z - 47 = 0
Invariants method
Given equation of the surface of 2-order:
$$9 x^{2} - 18 x - 36 y^{2} + 72 y + 4 z^{2} + 16 z - 47 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x z + 2 a_{14} x + a_{22} y^{2} + 2 a_{23} y z + 2 a_{24} y + a_{33} z^{2} + 2 a_{34} z + a_{44} = 0$$
where
$$a_{11} = 9$$
$$a_{12} = 0$$
$$a_{13} = 0$$
$$a_{14} = -9$$
$$a_{22} = -36$$
$$a_{23} = 0$$
$$a_{24} = 36$$
$$a_{33} = 4$$
$$a_{34} = 8$$
$$a_{44} = -47$$
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
$$I_{1} = -23$$
     |9   0 |   |-36  0|   |9  0|
I2 = |      | + |      | + |    |
     |0  -36|   | 0   4|   |0  4|

$$I_{3} = \left|\begin{matrix}9 & 0 & 0\\0 & -36 & 0\\0 & 0 & 4\end{matrix}\right|$$
$$I_{4} = \left|\begin{matrix}9 & 0 & 0 & -9\\0 & -36 & 0 & 36\\0 & 0 & 4 & 8\\-9 & 36 & 8 & -47\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}9 - \lambda & 0 & 0\\0 & - \lambda - 36 & 0\\0 & 0 & 4 - \lambda\end{matrix}\right|$$
     |9   -9 |   |-36  36 |   |4   8 |
K2 = |       | + |        | + |      |
     |-9  -47|   |36   -47|   |8  -47|

     |9    0   -9 |   |-36  0  36 |   |9   0  -9 |
     |            |   |           |   |          |
K3 = |0   -36  36 | + | 0   4   8 | + |0   4   8 |
     |            |   |           |   |          |
     |-9  36   -47|   |36   8  -47|   |-9  8  -47|

$$I_{1} = -23$$
$$I_{2} = -432$$
$$I_{3} = -1296$$
$$I_{4} = 46656$$
$$I{\left(\lambda \right)} = - \lambda^{3} - 23 \lambda^{2} + 432 \lambda - 1296$$
$$K_{2} = -360$$
$$K_{3} = 7776$$
Because
I3 != 0

then by type of surface:
you need to
Make the characteristic equation for the surface:
$$- I_{1} \lambda^{2} + I_{2} \lambda - I_{3} + \lambda^{3} = 0$$
or
$$\lambda^{3} + 23 \lambda^{2} - 432 \lambda + 1296 = 0$$
Solve this equation
$$\lambda_{1} = 9$$
$$\lambda_{2} = 4$$
$$\lambda_{3} = -36$$
then the canonical form of the equation will be
$$\left(\tilde z^{2} \lambda_{3} + \left(\tilde x^{2} \lambda_{1} + \tilde y^{2} \lambda_{2}\right)\right) + \frac{I_{4}}{I_{3}} = 0$$
$$9 \tilde x^{2} + 4 \tilde y^{2} - 36 \tilde z^{2} - 36 = 0$$
$$- \frac{\tilde z^{2}}{1^{2}} + \left(\frac{\tilde x^{2}}{2^{2}} + \frac{\tilde y^{2}}{3^{2}}\right) = 1$$
this equation is fora type one-sided hyperboloid
- reduced to canonical form