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3x^2-36x+3y^2-56y+85=0 canonical form

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                      2      2    
85 - 56*y - 36*x + 3*x  + 3*y  = 0
$$3 x^{2} - 36 x + 3 y^{2} - 56 y + 85 = 0$$
3*x^2 - 36*x + 3*y^2 - 56*y + 85 = 0
Detail solution
Given line equation of 2-order:
$$3 x^{2} - 36 x + 3 y^{2} - 56 y + 85 = 0$$
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
$$a_{11} = 3$$
$$a_{12} = 0$$
$$a_{13} = -18$$
$$a_{22} = 3$$
$$a_{23} = -28$$
$$a_{33} = 85$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}3 & 0\\0 & 3\end{matrix}\right|$$
$$\Delta = 9$$
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
$$3 x_{0} - 18 = 0$$
$$3 y_{0} - 28 = 0$$
then
$$x_{0} = 6$$
$$y_{0} = \frac{28}{3}$$
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
$$a'_{33} = - 18 x_{0} - 28 y_{0} + 85$$
$$a'_{33} = - \frac{853}{3}$$
then equation turns into
$$3 x'^{2} + 3 y'^{2} - \frac{853}{3} = 0$$
Given equation is circle
$$\frac{\tilde x^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{853} \sqrt{2559}}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{853} \sqrt{2559}}\right)^{2}} = 1$$
- reduced to canonical form
The center of canonical coordinate system at point O
(6, 28/3)

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:
$$3 x^{2} - 36 x + 3 y^{2} - 56 y + 85 = 0$$
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
$$a_{11} = 3$$
$$a_{12} = 0$$
$$a_{13} = -18$$
$$a_{22} = 3$$
$$a_{23} = -28$$
$$a_{33} = 85$$
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
$$I_{1} = 6$$
     |3  0|
I2 = |    |
     |0  3|

$$I_{3} = \left|\begin{matrix}3 & 0 & -18\\0 & 3 & -28\\-18 & -28 & 85\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}3 - \lambda & 0\\0 & 3 - \lambda\end{matrix}\right|$$
     | 3   -18|   | 3   -28|
K2 = |        | + |        |
     |-18  85 |   |-28  85 |

$$I_{1} = 6$$
$$I_{2} = 9$$
$$I_{3} = -2559$$
$$I{\left(\lambda \right)} = \lambda^{2} - 6 \lambda + 9$$
$$K_{2} = -598$$
Because
$$I_{2} > 0 \wedge I_{1} I_{3} < 0$$
then by line type:
this equation is of type : circle
Make the characteristic equation for the line:
$$- I_{1} \lambda + I_{2} + \lambda^{2} = 0$$
or
$$\lambda^{2} - 6 \lambda + 9 = 0$$
$$\lambda_{1} = 3$$
$$\lambda_{2} = 3$$
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
$$3 \tilde x^{2} + 3 \tilde y^{2} - \frac{853}{3} = 0$$
$$\frac{\tilde x^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{853} \sqrt{2559}}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\frac{1}{3} \sqrt{3}}{\frac{1}{853} \sqrt{2559}}\right)^{2}} = 1$$
- reduced to canonical form