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15x^2+6y^2-10z^2+90x-72y+60z+231=0 canonical form

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                 2      2       2                  
231 - 72*y - 10*z  + 6*y  + 15*x  + 60*z + 90*x = 0
$$15 x^{2} + 90 x + 6 y^{2} - 72 y - 10 z^{2} + 60 z + 231 = 0$$
15*x^2 + 90*x + 6*y^2 - 72*y - 10*z^2 + 60*z + 231 = 0
Invariants method
Given equation of the surface of 2-order:
$$15 x^{2} + 90 x + 6 y^{2} - 72 y - 10 z^{2} + 60 z + 231 = 0$$
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
$$a_{11} = 15$$
$$a_{12} = 0$$
$$a_{13} = 0$$
$$a_{14} = 45$$
$$a_{22} = 6$$
$$a_{23} = 0$$
$$a_{24} = -36$$
$$a_{33} = -10$$
$$a_{34} = 30$$
$$a_{44} = 231$$
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
$$I_{1} = 11$$
     |15  0|   |6   0 |   |15   0 |
I2 = |     | + |      | + |       |
     |0   6|   |0  -10|   |0   -10|

$$I_{3} = \left|\begin{matrix}15 & 0 & 0\\0 & 6 & 0\\0 & 0 & -10\end{matrix}\right|$$
$$I_{4} = \left|\begin{matrix}15 & 0 & 0 & 45\\0 & 6 & 0 & -36\\0 & 0 & -10 & 30\\45 & -36 & 30 & 231\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}15 - \lambda & 0 & 0\\0 & 6 - \lambda & 0\\0 & 0 & - \lambda - 10\end{matrix}\right|$$
     |15  45 |   | 6   -36|   |-10  30 |
K2 = |       | + |        | + |        |
     |45  231|   |-36  231|   |30   231|

     |15   0   45 |   | 6    0   -36|   |15   0   45 |
     |            |   |             |   |            |
K3 = |0    6   -36| + | 0   -10  30 | + |0   -10  30 |
     |            |   |             |   |            |
     |45  -36  231|   |-36  30   231|   |45  30   231|

$$I_{1} = 11$$
$$I_{2} = -120$$
$$I_{3} = -900$$
$$I_{4} = 27000$$
$$I{\left(\lambda \right)} = - \lambda^{3} + 11 \lambda^{2} + 120 \lambda - 900$$
$$K_{2} = -1680$$
$$K_{3} = -45000$$
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
$$\lambda^{3} - 11 \lambda^{2} - 120 \lambda + 900 = 0$$
$$\lambda_{1} = 15$$
$$\lambda_{2} = 6$$
$$\lambda_{3} = -10$$
then the canonical form of the equation will be
$$\left(\tilde z^{2} \lambda_{3} + \left(\tilde x^{2} \lambda_{1} + \tilde y^{2} \lambda_{2}\right)\right) + \frac{I_{4}}{I_{3}} = 0$$
$$15 \tilde x^{2} + 6 \tilde y^{2} - 10 \tilde z^{2} - 30 = 0$$
$$- \frac{\tilde z^{2}}{\left(\frac{\frac{1}{10} \sqrt{10}}{\frac{1}{30} \sqrt{30}}\right)^{2}} + \left(\frac{\tilde x^{2}}{\left(\frac{\frac{1}{15} \sqrt{15}}{\frac{1}{30} \sqrt{30}}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\frac{1}{6} \sqrt{6}}{\frac{1}{30} \sqrt{30}}\right)^{2}}\right) = 1$$
this equation is fora type one-sided hyperboloid
- reduced to canonical form