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x^2-8x+y^2+2y=-7 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
 2          2           
x  - 8*x + y  + 2*y = -7
$$2 y + \left(y^{2} + \left(x^{2} - 8 x\right)\right) = -7$$
Solución detallada
Transportemos el miembro derecho de la ecuación al
miembro izquierdo de la ecuación con el signo negativo.

La ecuación se convierte de
$$2 y + \left(y^{2} + \left(x^{2} - 8 x\right)\right) = -7$$
en
$$\left(2 y + \left(y^{2} + \left(x^{2} - 8 x\right)\right)\right) + 7 = 0$$
Es la ecuación de la forma
a*x^2 + b*x + c = 0

La ecuación cuadrática puede ser resuelta
con la ayuda del discriminante.
Las raíces de la ecuación cuadrática:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
donde D = b^2 - 4*a*c es el discriminante.
Como
$$a = 1$$
$$b = -8$$
$$c = y^{2} + 2 y + 7$$
, entonces
D = b^2 - 4 * a * c = 

(-8)^2 - 4 * (1) * (7 + y^2 + 2*y) = 36 - 8*y - 4*y^2

La ecuación tiene dos raíces.
x1 = (-b + sqrt(D)) / (2*a)

x2 = (-b - sqrt(D)) / (2*a)

o
$$x_{1} = \frac{\sqrt{- 4 y^{2} - 8 y + 36}}{2} + 4$$
$$x_{2} = 4 - \frac{\sqrt{- 4 y^{2} - 8 y + 36}}{2}$$
Teorema de Cardano-Vieta
es ecuación cuadrática reducida
$$p x + q + x^{2} = 0$$
donde
$$p = \frac{b}{a}$$
$$p = -8$$
$$q = \frac{c}{a}$$
$$q = y^{2} + 2 y + 7$$
Fórmulas de Cardano-Vieta
$$x_{1} + x_{2} = - p$$
$$x_{1} x_{2} = q$$
$$x_{1} + x_{2} = 8$$
$$x_{1} x_{2} = y^{2} + 2 y + 7$$
Gráfica
Suma y producto de raíces [src]
suma
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       /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\          /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\
    4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|       4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|
4 - \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| - I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------| + 4 + \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| + I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------|
                                                                            \                              2                               /                                                                             \                              2                               /                                                                               \                              2                               /                                                                             \                              2                               /
$$\left(- i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} - \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4\right) + \left(i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4\right)$$
=
8
$$8$$
producto
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|       /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\| |       /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\|
|    4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|| |    4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/||
|4 - \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| - I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------||*|4 + \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| + I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------||
\                                                                            \                              2                               /                                                                             \                              2                               // \                                                                            \                              2                               /                                                                             \                              2                               //
$$\left(- i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} - \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4\right) \left(i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4\right)$$
=
      2        2                                           
7 + re (y) - im (y) + 2*re(y) + 2*I*im(y) + 2*I*im(y)*re(y)
$$\left(\operatorname{re}{\left(y\right)}\right)^{2} + 2 i \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} + 2 \operatorname{re}{\left(y\right)} - \left(\operatorname{im}{\left(y\right)}\right)^{2} + 2 i \operatorname{im}{\left(y\right)} + 7$$
7 + re(y)^2 - im(y)^2 + 2*re(y) + 2*i*im(y) + 2*i*im(y)*re(y)
Respuesta rápida [src]
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            /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\
         4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|
x1 = 4 - \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| - I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------|
                                                                                 \                              2                               /                                                                             \                              2                               /
$$x_{1} = - i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} - \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4$$
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            /                                                              2     /     /                                2        2             \\        /                                                              2     /     /                                2        2             \\
         4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|     4 /                            2   /      2        2             \      |atan2\-2*im(y) - 2*im(y)*re(y), 9 + im (y) - re (y) - 2*re(y)/|
x2 = 4 + \/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *cos|--------------------------------------------------------------| + I*\/   (-2*im(y) - 2*im(y)*re(y))  + \9 + im (y) - re (y) - 2*re(y)/  *sin|--------------------------------------------------------------|
                                                                                 \                              2                               /                                                                             \                              2                               /
$$x_{2} = i \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \sin{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + \sqrt[4]{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)}\right)^{2} + \left(- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9\right)^{2}} \cos{\left(\frac{\operatorname{atan_{2}}{\left(- 2 \operatorname{re}{\left(y\right)} \operatorname{im}{\left(y\right)} - 2 \operatorname{im}{\left(y\right)},- \left(\operatorname{re}{\left(y\right)}\right)^{2} - 2 \operatorname{re}{\left(y\right)} + \left(\operatorname{im}{\left(y\right)}\right)^{2} + 9 \right)}}{2} \right)} + 4$$
x2 = i*((-2*re(y)*im(y) - 2*im(y))^2 + (-re(y)^2 - 2*re(y) + im(y)^2 + 9)^2)^(1/4)*sin(atan2(-2*re(y)*im(y) - 2*im(y, -re(y)^2 - 2*re(y) + im(y)^2 + 9)/2) + ((-2*re(y)*im(y) - 2*im(y))^2 + (-re(y)^2 - 2*re(y) + im(y)^2 + 9)^2)^(1/4)*cos(atan2(-2*re(y)*im(y) - 2*im(y), -re(y)^2 - 2*re(y) + im(y)^2 + 9)/2) + 4)