Given line equation of 2-order:
$$25 x^{2} - 30 x y + 68 x + 9 y^{2} + 19 = 0$$
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
$$a_{11} = 25$$
$$a_{12} = -15$$
$$a_{13} = 34$$
$$a_{22} = 9$$
$$a_{23} = 0$$
$$a_{33} = 19$$
To calculate the determinant
$$\Delta = \left|\begin{matrix}a_{11} & a_{12}\\a_{12} & a_{22}\end{matrix}\right|$$
or, substitute
$$\Delta = \left|\begin{matrix}25 & -15\\-15 & 9\end{matrix}\right|$$
$$\Delta = 0$$
Because
$$\Delta$$
is equal to 0, then
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
$$\cot{\left(2 \phi \right)} = - \frac{8}{15}$$
then
$$\phi = - \frac{\operatorname{acot}{\left(\frac{8}{15} \right)}}{2}$$
$$\sin{\left(2 \phi \right)} = - \frac{15}{17}$$
$$\cos{\left(2 \phi \right)} = \frac{8}{17}$$
$$\cos{\left(\phi \right)} = \sqrt{\frac{\cos{\left(2 \phi \right)}}{2} + \frac{1}{2}}$$
$$\sin{\left(\phi \right)} = \sqrt{1 - \cos^{2}{\left(\phi \right)}}$$
$$\cos{\left(\phi \right)} = \frac{5 \sqrt{34}}{34}$$
$$\sin{\left(\phi \right)} = - \frac{3 \sqrt{34}}{34}$$
substitute coefficients
$$x' = \frac{5 \sqrt{34} \tilde x}{34} + \frac{3 \sqrt{34} \tilde y}{34}$$
$$y' = - \frac{3 \sqrt{34} \tilde x}{34} + \frac{5 \sqrt{34} \tilde y}{34}$$
then the equation turns from
$$25 x'^{2} - 30 x' y' + 68 x' + 9 y'^{2} + 19 = 0$$
to
$$9 \left(- \frac{3 \sqrt{34} \tilde x}{34} + \frac{5 \sqrt{34} \tilde y}{34}\right)^{2} - 30 \left(- \frac{3 \sqrt{34} \tilde x}{34} + \frac{5 \sqrt{34} \tilde y}{34}\right) \left(\frac{5 \sqrt{34} \tilde x}{34} + \frac{3 \sqrt{34} \tilde y}{34}\right) + 25 \left(\frac{5 \sqrt{34} \tilde x}{34} + \frac{3 \sqrt{34} \tilde y}{34}\right)^{2} + 68 \left(\frac{5 \sqrt{34} \tilde x}{34} + \frac{3 \sqrt{34} \tilde y}{34}\right) + 19 = 0$$
simplify
$$34 \tilde x^{2} + 10 \sqrt{34} \tilde x + 6 \sqrt{34} \tilde y + 19 = 0$$
$$\left(\sqrt{34} \tilde x + 5\right)^{2} = - 6 \sqrt{34} \tilde y + 6$$
$$\left(\tilde x + \frac{5 \sqrt{34}}{34}\right)^{2} = - \frac{3 \sqrt{34} \left(\tilde y - \frac{\sqrt{34}}{34}\right)}{17}$$
$$\tilde x'^{2} = - \frac{3 \sqrt{34} \tilde y'}{17}$$
Given equation is by parabola
- reduced to canonical form
The center of the canonical coordinate system in OXY
$$x_{0} = \tilde x \cos{\left(\phi \right)} - \tilde y \sin{\left(\phi \right)}$$
$$y_{0} = \tilde x \sin{\left(\phi \right)} + \tilde y \cos{\left(\phi \right)}$$
$$x_{0} = 0 \frac{5 \sqrt{34}}{34} + 0 \left(- \frac{3 \sqrt{34}}{34}\right)$$
$$y_{0} = 0 \left(- \frac{3 \sqrt{34}}{34}\right) + 0 \frac{5 \sqrt{34}}{34}$$
$$x_{0} = 0$$
$$y_{0} = 0$$
The center of canonical coordinate system at point O
(0, 0)
Basis of the canonical coordinate system
$$\vec e_1 = \left( \frac{5 \sqrt{34}}{34}, \ - \frac{3 \sqrt{34}}{34}\right)$$
$$\vec e_2 = \left( \frac{3 \sqrt{34}}{34}, \ \frac{5 \sqrt{34}}{34}\right)$$