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14x^2-7y^2+20xy-8x-34y-35 canonical form

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                      2       2             
-35 - 34*y - 8*x - 7*y  + 14*x  + 20*x*y = 0
$$14 x^{2} + 20 x y - 8 x - 7 y^{2} - 34 y - 35 = 0$$
14*x^2 + 20*x*y - 8*x - 7*y^2 - 34*y - 35 = 0
Detail solution
Given line equation of 2-order:
$$14 x^{2} + 20 x y - 8 x - 7 y^{2} - 34 y - 35 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x + a_{22} y^{2} + 2 a_{23} y + a_{33} = 0$$
where
$$a_{11} = 14$$
$$a_{12} = 10$$
$$a_{13} = -4$$
$$a_{22} = -7$$
$$a_{23} = -17$$
$$a_{33} = -35$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}14 & 10\\10 & -7\end{matrix}\right|$$
$$\Delta = -198$$
Because
$$\Delta$$
is not equal to 0, then
find the center of the canonical coordinate system. To do it, solve the system of equations
$$a_{11} x_{0} + a_{12} y_{0} + a_{13} = 0$$
$$a_{12} x_{0} + a_{22} y_{0} + a_{23} = 0$$
substitute coefficients
$$14 x_{0} + 10 y_{0} - 4 = 0$$
$$10 x_{0} - 7 y_{0} - 17 = 0$$
then
$$x_{0} = 1$$
$$y_{0} = -1$$
Thus, we have the equation in the coordinate system O'x'y'
$$a'_{33} + a_{11} x'^{2} + 2 a_{12} x' y' + a_{22} y'^{2} = 0$$
where
$$a'_{33} = a_{13} x_{0} + a_{23} y_{0} + a_{33}$$
or
$$a'_{33} = - 4 x_{0} - 17 y_{0} - 35$$
$$a'_{33} = -22$$
then equation turns into
$$14 x'^{2} + 20 x' y' - 7 y'^{2} - 22 = 0$$
Rotate the resulting coordinate system by an angle φ
$$x' = \tilde x \cos{\left(\phi \right)} - \tilde y \sin{\left(\phi \right)}$$
$$y' = \tilde x \sin{\left(\phi \right)} + \tilde y \cos{\left(\phi \right)}$$
φ - determined from the formula
$$\cot{\left(2 \phi \right)} = \frac{a_{11} - a_{22}}{2 a_{12}}$$
substitute coefficients
$$\cot{\left(2 \phi \right)} = \frac{21}{20}$$
then
$$\phi = \frac{\operatorname{acot}{\left(\frac{21}{20} \right)}}{2}$$
$$\sin{\left(2 \phi \right)} = \frac{20}{29}$$
$$\cos{\left(2 \phi \right)} = \frac{21}{29}$$
$$\cos{\left(\phi \right)} = \sqrt{\frac{\cos{\left(2 \phi \right)}}{2} + \frac{1}{2}}$$
$$\sin{\left(\phi \right)} = \sqrt{1 - \cos^{2}{\left(\phi \right)}}$$
$$\cos{\left(\phi \right)} = \frac{5 \sqrt{29}}{29}$$
$$\sin{\left(\phi \right)} = \frac{2 \sqrt{29}}{29}$$
substitute coefficients
$$x' = \frac{5 \sqrt{29} \tilde x}{29} - \frac{2 \sqrt{29} \tilde y}{29}$$
$$y' = \frac{2 \sqrt{29} \tilde x}{29} + \frac{5 \sqrt{29} \tilde y}{29}$$
then the equation turns from
$$14 x'^{2} + 20 x' y' - 7 y'^{2} - 22 = 0$$
to
$$- 7 \left(\frac{2 \sqrt{29} \tilde x}{29} + \frac{5 \sqrt{29} \tilde y}{29}\right)^{2} + 20 \left(\frac{2 \sqrt{29} \tilde x}{29} + \frac{5 \sqrt{29} \tilde y}{29}\right) \left(\frac{5 \sqrt{29} \tilde x}{29} - \frac{2 \sqrt{29} \tilde y}{29}\right) + 14 \left(\frac{5 \sqrt{29} \tilde x}{29} - \frac{2 \sqrt{29} \tilde y}{29}\right)^{2} - 22 = 0$$
simplify
$$18 \tilde x^{2} - 11 \tilde y^{2} - 22 = 0$$
$$- 18 \tilde x^{2} + 11 \tilde y^{2} + 22 = 0$$
Given equation is hyperbole
$$\frac{\tilde x^{2}}{\frac{11}{9}} - \frac{\tilde y^{2}}{2} = 1$$
- reduced to canonical form
The center of canonical coordinate system at point O
(1, -1)

Basis of the canonical coordinate system
$$\vec e_1 = \left( \frac{5 \sqrt{29}}{29}, \ \frac{2 \sqrt{29}}{29}\right)$$
$$\vec e_2 = \left( - \frac{2 \sqrt{29}}{29}, \ \frac{5 \sqrt{29}}{29}\right)$$
Invariants method
Given line equation of 2-order:
$$14 x^{2} + 20 x y - 8 x - 7 y^{2} - 34 y - 35 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + 2 a_{13} x + a_{22} y^{2} + 2 a_{23} y + a_{33} = 0$$
where
$$a_{11} = 14$$
$$a_{12} = 10$$
$$a_{13} = -4$$
$$a_{22} = -7$$
$$a_{23} = -17$$
$$a_{33} = -35$$
The invariants of the equation when converting coordinates are determinants:
$$I_{1} = a_{11} + a_{22}$$
     |a11  a12|
I2 = |        |
     |a12  a22|

$$I_{3} = \left|\begin{matrix}a_{11} & a_{12} & a_{13}\\a_{12} & a_{22} & a_{23}\\a_{13} & a_{23} & a_{33}\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}a_{11} - \lambda & a_{12}\\a_{12} & a_{22} - \lambda\end{matrix}\right|$$
     |a11  a13|   |a22  a23|
K2 = |        | + |        |
     |a13  a33|   |a23  a33|

substitute coefficients
$$I_{1} = 7$$
     |14  10|
I2 = |      |
     |10  -7|

$$I_{3} = \left|\begin{matrix}14 & 10 & -4\\10 & -7 & -17\\-4 & -17 & -35\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}14 - \lambda & 10\\10 & - \lambda - 7\end{matrix}\right|$$
     |14  -4 |   |-7   -17|
K2 = |       | + |        |
     |-4  -35|   |-17  -35|

$$I_{1} = 7$$
$$I_{2} = -198$$
$$I_{3} = 4356$$
$$I{\left(\lambda \right)} = \lambda^{2} - 7 \lambda - 198$$
$$K_{2} = -550$$
Because
$$I_{2} < 0 \wedge I_{3} \neq 0$$
then by line type:
this equation is of type : hyperbola
Make the characteristic equation for the line:
$$- I_{1} \lambda + I_{2} + \lambda^{2} = 0$$
or
$$\lambda^{2} - 7 \lambda - 198 = 0$$
$$\lambda_{1} = 18$$
$$\lambda_{2} = -11$$
then the canonical form of the equation will be
$$\tilde x^{2} \lambda_{1} + \tilde y^{2} \lambda_{2} + \frac{I_{3}}{I_{2}} = 0$$
or
$$18 \tilde x^{2} - 11 \tilde y^{2} - 22 = 0$$
$$\frac{\tilde x^{2}}{\frac{11}{9}} - \frac{\tilde y^{2}}{2} = 1$$
- reduced to canonical form