Mister Exam

Other calculators


x^2+8y^2+8x+14y+5=0

x^2+8y^2+8x+14y+5=0 canonical form

The teacher will be very surprised to see your correct solution 😉

v

The graph:

x: [, ]
y: [, ]
z: [, ]

Quality:

 (Number of points on the axis)

Plot type:

The solution

You have entered [src]
     2            2           
5 + x  + 8*x + 8*y  + 14*y = 0
$$x^{2} + 8 y^{2} + 8 x + 14 y + 5 = 0$$
x^2 + 8*x + 8*y^2 + 14*y + 5 = 0
Detail solution
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
$$\vec e_{1} = \left( 1, \ 0\right)$$
$$\vec e_{2} = \left( 0, \ 1\right)$$
Invariants method
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
$$a_{11} = 1$$
$$a_{12} = 0$$
$$a_{13} = 4$$
$$a_{22} = 8$$
$$a_{23} = 7$$
$$a_{33} = 5$$
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
$$I_{1} = 9$$
     |1  0|
I2 = |    |
     |0  8|

$$I_{3} = \left|\begin{matrix}1 & 0 & 4\\0 & 8 & 7\\4 & 7 & 5\end{matrix}\right|$$
$$I{\left(\lambda \right)} = \left|\begin{matrix}- \lambda + 1 & 0\\0 & - \lambda + 8\end{matrix}\right|$$
     |1  4|   |8  7|
K2 = |    | + |    |
     |4  5|   |7  5|

$$I_{1} = 9$$
$$I_{2} = 8$$
$$I_{3} = -137$$
$$I{\left(\lambda \right)} = \lambda^{2} - 9 \lambda + 8$$
$$K_{2} = -20$$
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:
$$- I_{1} \lambda + \lambda^{2} + I_{2} = 0$$
or
$$\lambda^{2} - 9 \lambda + 8 = 0$$
Solve this equation
$$\lambda_{1} = 8$$
$$\lambda_{2} = 1$$
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
$$8 \tilde x^{2} + \tilde y^{2} - \frac{137}{8} = 0$$
$$\frac{\tilde x^{2}}{\left(\frac{\sqrt{137}}{8}\right)^{2}} + \frac{\tilde y^{2}}{\left(\frac{\sqrt{274}}{4}\right)^{2}} = 1$$
- reduced to canonical form
The graph
x^2+8y^2+8x+14y+5=0 canonical form