Given line equation of 2-order:
$$x^{2} + 8 y^{2} + 8 x + 14 y + 5 = 0$$
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
$$a_{11} = 1$$
$$a_{12} = 0$$
$$a_{13} = 4$$
$$a_{22} = 8$$
$$a_{23} = 7$$
$$a_{33} = 5$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}1 & 0\\0 & 8\end{matrix}\right|$$
$$\Delta = 8$$
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
$$x_{0} + 4 = 0$$
$$8 y_{0} + 7 = 0$$
then
$$x_{0} = -4$$
$$y_{0} = - \frac{7}{8}$$
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
$$a'_{33} = 4 x_{0} + 7 y_{0} + 5$$
$$a'_{33} = - \frac{137}{8}$$
then The equation is transformed to
$$x'^{2} + 8 y'^{2} - \frac{137}{8} = 0$$
Given equation is ellipse
$$\frac{\tilde x^{2}}{\left(\frac{\sqrt{274}}{4}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\sqrt{137}}{8}\right)^{2}} = 1$$
- reduced to canonical form
The center of canonical coordinate system at point O
(-4, -7/8)
Basis of the canonical coordinate system
$$\vec e_{1} = \left( 1, \ 0\right)$$
$$\vec e_{2} = \left( 0, \ 1\right)$$