Se da la ecuación de superficie de 2 grado:
$$3 x^{2} - 6 \sqrt{2} x + 3 y^{2} + 2 \sqrt{3} y - 3 z^{2} + 2 \sqrt{6} z + 8 = 0$$
Esta ecuación tiene la forma:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x z + 2 a_{14} x + a_{22} y^{2} + 2 a_{23} y z + 2 a_{24} y + a_{33} z^{2} + 2 a_{34} z + a_{44} = 0$$
donde
$$a_{11} = 3$$
$$a_{12} = 0$$
$$a_{13} = 0$$
$$a_{14} = - 3 \sqrt{2}$$
$$a_{22} = 3$$
$$a_{23} = 0$$
$$a_{24} = \sqrt{3}$$
$$a_{33} = -3$$
$$a_{34} = \sqrt{6}$$
$$a_{44} = 8$$
Las invariantes de esta ecuación al transformar las coordenadas son los determinantes:
$$I_{1} = a_{11} + a_{22} + a_{33}$$
|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|
sustituimos coeficientes
$$I_{1} = 3$$
|3 0| |3 0 | |3 0 |
I2 = | | + | | + | |
|0 3| |0 -3| |0 -3|
$$I_{3} = \left|\begin{matrix}3 & 0 & 0\\0 & 3 & 0\\0 & 0 & -3\end{matrix}\right|$$
$$I_{4} = \left|\begin{matrix}3 & 0 & 0 & - 3 \sqrt{2}\\0 & 3 & 0 & \sqrt{3}\\0 & 0 & -3 & \sqrt{6}\\- 3 \sqrt{2} & \sqrt{3} & \sqrt{6} & 8\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}3 - \lambda & 0 & 0\\0 & 3 - \lambda & 0\\0 & 0 & - \lambda - 3\end{matrix}\right|$$
| ___| | ___| | ___|
| 3 -3*\/ 2 | | 3 \/ 3 | | -3 \/ 6 |
K2 = | | + | | + | |
| ___ | | ___ | | ___ |
|-3*\/ 2 8 | |\/ 3 8 | |\/ 6 8 |
| ___| | ___| | ___|
| 3 0 -3*\/ 2 | | 3 0 \/ 3 | | 3 0 -3*\/ 2 |
| | | | | |
| ___ | | ___| | ___ |
K3 = | 0 3 \/ 3 | + | 0 -3 \/ 6 | + | 0 -3 \/ 6 |
| | | | | |
| ___ ___ | | ___ ___ | | ___ ___ |
|-3*\/ 2 \/ 3 8 | |\/ 3 \/ 6 8 | |-3*\/ 2 \/ 6 8 |
$$I_{1} = 3$$
$$I_{2} = -9$$
$$I_{3} = -27$$
$$I_{4} = -81$$
$$I{\left(\lambda \right)} = - \lambda^{3} + 3 \lambda^{2} + 9 \lambda - 27$$
$$K_{2} = -3$$
$$K_{3} = -108$$
Como
I3 != 0
entonces por razón de tipos de rectas:
hay que
Formulamos la ecuación característica para nuestra superficie:
$$- I_{1} \lambda^{2} + I_{2} \lambda - I_{3} + \lambda^{3} = 0$$
o
$$\lambda^{3} - 3 \lambda^{2} - 9 \lambda + 27 = 0$$
$$\lambda_{1} = -3$$
$$\lambda_{2} = 3$$
$$\lambda_{3} = 3$$
entonces la forma canónica de la ecuación será
$$\left(\tilde z^{2} \lambda_{3} + \left(\tilde x^{2} \lambda_{1} + \tilde y^{2} \lambda_{2}\right)\right) + \frac{I_{4}}{I_{3}} = 0$$
$$- 3 \tilde x^{2} + 3 \tilde y^{2} + 3 \tilde z^{2} + 3 = 0$$
$$- \frac{\tilde x^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{3} \sqrt{3}}\right)^{2}} + \left(\frac{\tilde y^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{3} \sqrt{3}}\right)^{2}} + \frac{\tilde z^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{3} \sqrt{3}}\right)^{2}}\right) = -1$$
es la ecuación para el tipo hiperboloide bilateral
- está reducida a la forma canónica