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4x^2-9y^2-8x+36y-68=0

4x^2-9y^2-8x+36y-68=0 canonical form

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         2            2           
-68 - 9*y  - 8*x + 4*x  + 36*y = 0
$$4 x^{2} - 9 y^{2} - 8 x + 36 y - 68 = 0$$
4*x^2 - 8*x - 9*y^2 + 36*y - 68 = 0
Detail solution
Given line equation of 2-order:
$$4 x^{2} - 9 y^{2} - 8 x + 36 y - 68 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + a_{22} y^{2} + 2 a_{13} x + 2 a_{23} y + a_{33} = 0$$
where
$$a_{11} = 4$$
$$a_{12} = 0$$
$$a_{13} = -4$$
$$a_{22} = -9$$
$$a_{23} = 18$$
$$a_{33} = -68$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}4 & 0\\0 & -9\end{matrix}\right|$$
$$\Delta = -36$$
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
$$4 x_{0} - 4 = 0$$
$$- 9 y_{0} + 18 = 0$$
then
$$x_{0} = 1$$
$$y_{0} = 2$$
Thus, we have the equation in the coordinate system O'x'y'
$$a_{11} x'^{2} + 2 a_{12} x' y' + a_{22} y'^{2} + a'_{33} = 0$$
where
$$a'_{33} = a_{13} x_{0} + a_{23} y_{0} + a_{33}$$
or
$$a'_{33} = - 4 x_{0} + 18 y_{0} - 68$$
$$a'_{33} = -36$$
then The equation is transformed to
$$4 x'^{2} - 9 y'^{2} - 36 = 0$$
Given equation is hyperbole
$$\frac{\tilde x^{2}}{9} - \frac{\tilde y^{2}}{4} = 1$$
- reduced to canonical form
The center of canonical coordinate system at point O
(1, 2)

Basis of the canonical coordinate system
$$\vec e_{1} = \left( 1, \ 0\right)$$
$$\vec e_{2} = \left( 0, \ 1\right)$$
Invariants method
Given line equation of 2-order:
$$4 x^{2} - 9 y^{2} - 8 x + 36 y - 68 = 0$$
This equation looks like:
$$a_{11} x^{2} + 2 a_{12} x y + a_{22} y^{2} + 2 a_{13} x + 2 a_{23} y + a_{33} = 0$$
where
$$a_{11} = 4$$
$$a_{12} = 0$$
$$a_{13} = -4$$
$$a_{22} = -9$$
$$a_{23} = 18$$
$$a_{33} = -68$$
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
$$I_{1} = -5$$
     |4  0 |
I2 = |     |
     |0  -9|

$$I_{3} = \left|\begin{matrix}4 & 0 & -4\\0 & -9 & 18\\-4 & 18 & -68\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}- \lambda + 4 & 0\\0 & - \lambda - 9\end{matrix}\right|$$
     |4   -4 |   |-9  18 |
K2 = |       | + |       |
     |-4  -68|   |18  -68|

$$I_{1} = -5$$
$$I_{2} = -36$$
$$I_{3} = 1296$$
$$I{\left(\lambda \right)} = \lambda^{2} + 5 \lambda - 36$$
$$K_{2} = 0$$
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:
$$- I_{1} \lambda + \lambda^{2} + I_{2} = 0$$
or
$$\lambda^{2} + 5 \lambda - 36 = 0$$
Solve this equation
$$\lambda_{1} = 4$$
$$\lambda_{2} = -9$$
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
$$4 \tilde x^{2} - 9 \tilde y^{2} - 36 = 0$$
$$\frac{\tilde x^{2}}{9} - \frac{\tilde y^{2}}{4} = 1$$
- reduced to canonical form
The graph
4x^2-9y^2-8x+36y-68=0 canonical form