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8x^2+5y^2+15x+6y-7=0

8x^2+5y^2+15x+6y-7=0 canonical form

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        2            2           
-7 + 5*y  + 6*y + 8*x  + 15*x = 0
$$8 x^{2} + 15 x + 5 y^{2} + 6 y - 7 = 0$$
8*x^2 + 15*x + 5*y^2 + 6*y - 7 = 0
Detail solution
Given line equation of 2-order:
$$8 x^{2} + 15 x + 5 y^{2} + 6 y - 7 = 0$$
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
$$a_{11} = 8$$
$$a_{12} = 0$$
$$a_{13} = \frac{15}{2}$$
$$a_{22} = 5$$
$$a_{23} = 3$$
$$a_{33} = -7$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}8 & 0\\0 & 5\end{matrix}\right|$$
$$\Delta = 40$$
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
$$8 x_{0} + \frac{15}{2} = 0$$
$$5 y_{0} + 3 = 0$$
then
$$x_{0} = - \frac{15}{16}$$
$$y_{0} = - \frac{3}{5}$$
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
$$a'_{33} = \frac{15 x_{0}}{2} + 3 y_{0} - 7$$
$$a'_{33} = - \frac{2533}{160}$$
then equation turns into
$$8 x'^{2} + 5 y'^{2} - \frac{2533}{160} = 0$$
Given equation is ellipse
$$\frac{\tilde x^{2}}{\left(\frac{\sqrt{12665}}{80}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\sqrt{5066}}{40}\right)^{2}} = 1$$
- reduced to canonical form
The center of canonical coordinate system at point O
 -15        
(----, -3/5)
  16        

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:
$$8 x^{2} + 15 x + 5 y^{2} + 6 y - 7 = 0$$
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
$$a_{11} = 8$$
$$a_{12} = 0$$
$$a_{13} = \frac{15}{2}$$
$$a_{22} = 5$$
$$a_{23} = 3$$
$$a_{33} = -7$$
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
$$I_{1} = 13$$
     |8  0|
I2 = |    |
     |0  5|

$$I_{3} = \left|\begin{matrix}8 & 0 & \frac{15}{2}\\0 & 5 & 3\\\frac{15}{2} & 3 & -7\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}8 - \lambda & 0\\0 & 5 - \lambda\end{matrix}\right|$$
     | 8    15/2|   |5  3 |
K2 = |          | + |     |
     |15/2   -7 |   |3  -7|

$$I_{1} = 13$$
$$I_{2} = 40$$
$$I_{3} = - \frac{2533}{4}$$
$$I{\left(\lambda \right)} = \lambda^{2} - 13 \lambda + 40$$
$$K_{2} = - \frac{625}{4}$$
Because
$$I_{2} > 0 \wedge I_{1} I_{3} < 0$$
then by line type:
this equation is of type : ellipse
Make the characteristic equation for the line:
$$- I_{1} \lambda + I_{2} + \lambda^{2} = 0$$
or
$$\lambda^{2} - 13 \lambda + 40 = 0$$
Solve this equation
$$\lambda_{1} = 8$$
$$\lambda_{2} = 5$$
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
$$8 \tilde x^{2} + 5 \tilde y^{2} - \frac{2533}{160} = 0$$
$$\frac{\tilde x^{2}}{\left(\frac{\sqrt{12665}}{80}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\sqrt{5066}}{40}\right)^{2}} = 1$$
- reduced to canonical form
The graph
8x^2+5y^2+15x+6y-7=0 canonical form