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x^3+2*x^2-5x+9=0 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
 3      2              
x  + 2*x  - 5*x + 9 = 0
$$\left(- 5 x + \left(x^{3} + 2 x^{2}\right)\right) + 9 = 0$$
Teorema de Cardano-Vieta
es ecuación cúbica reducida
$$p x^{2} + q x + v + x^{3} = 0$$
donde
$$p = \frac{b}{a}$$
$$p = 2$$
$$q = \frac{c}{a}$$
$$q = -5$$
$$v = \frac{d}{a}$$
$$v = 9$$
Fórmulas de Cardano-Vieta
$$x_{1} + x_{2} + x_{3} = - p$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = q$$
$$x_{1} x_{2} x_{3} = v$$
$$x_{1} + x_{2} + x_{3} = -2$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = -5$$
$$x_{1} x_{2} x_{3} = 9$$
Gráfica
Respuesta rápida [src]
                __________________                                 /                                         __________________\
               /           ______                                  |                                        /           ______ |
              /  349   9*\/ 1165                                   |                                ___    /  349   9*\/ 1165  |
           3 /   --- + ----------                                  |                ___           \/ 3 *3 /   --- + ---------- |
       2   \/     2        2                     19                |           19*\/ 3                  \/     2        2      |
x1 = - - + ----------------------- + ------------------------- + I*|- ------------------------- + -----------------------------|
       3              6                     __________________     |         __________________                 6              |
                                           /           ______      |        /           ______                                 |
                                          /  349   9*\/ 1165       |       /  349   9*\/ 1165                                  |
                                     6*3 /   --- + ----------      |  6*3 /   --- + ----------                                 |
                                       \/     2        2           \    \/     2        2                                      /
$$x_{1} = - \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6}\right)$$
                __________________                                 /             __________________                            \
               /           ______                                  |            /           ______                             |
              /  349   9*\/ 1165                                   |    ___    /  349   9*\/ 1165                              |
           3 /   --- + ----------                                  |  \/ 3 *3 /   --- + ----------                  ___        |
       2   \/     2        2                     19                |        \/     2        2                  19*\/ 3         |
x2 = - - + ----------------------- + ------------------------- + I*|- ----------------------------- + -------------------------|
       3              6                     __________________     |                6                        __________________|
                                           /           ______      |                                        /           ______ |
                                          /  349   9*\/ 1165       |                                       /  349   9*\/ 1165  |
                                     6*3 /   --- + ----------      |                                  6*3 /   --- + ---------- |
                                       \/     2        2           \                                    \/     2        2      /
$$x_{2} = - \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}\right)$$
                                            __________________
                                           /           ______ 
                                          /  349   9*\/ 1165  
                                       3 /   --- + ---------- 
       2               19              \/     2        2      
x3 = - - - ------------------------- - -----------------------
       3          __________________              3           
                 /           ______                           
                /  349   9*\/ 1165                            
           3*3 /   --- + ----------                           
             \/     2        2                                
$$x_{3} = - \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{3} - \frac{19}{3 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} - \frac{2}{3}$$
x3 = -(9*sqrt(1165)/2 + 349/2)^(1/3)/3 - 19/(3*(9*sqrt(1165)/2 + 349/2)^(1/3)) - 2/3
Suma y producto de raíces [src]
suma
           __________________                                 /                                         __________________\              __________________                                 /             __________________                            \                                          __________________
          /           ______                                  |                                        /           ______ |             /           ______                                  |            /           ______                             |                                         /           ______ 
         /  349   9*\/ 1165                                   |                                ___    /  349   9*\/ 1165  |            /  349   9*\/ 1165                                   |    ___    /  349   9*\/ 1165                              |                                        /  349   9*\/ 1165  
      3 /   --- + ----------                                  |                ___           \/ 3 *3 /   --- + ---------- |         3 /   --- + ----------                                  |  \/ 3 *3 /   --- + ----------                  ___        |                                     3 /   --- + ---------- 
  2   \/     2        2                     19                |           19*\/ 3                  \/     2        2      |     2   \/     2        2                     19                |        \/     2        2                  19*\/ 3         |     2               19              \/     2        2      
- - + ----------------------- + ------------------------- + I*|- ------------------------- + -----------------------------| + - - + ----------------------- + ------------------------- + I*|- ----------------------------- + -------------------------| + - - - ------------------------- - -----------------------
  3              6                     __________________     |         __________________                 6              |     3              6                     __________________     |                6                        __________________|     3          __________________              3           
                                      /           ______      |        /           ______                                 |                                         /           ______      |                                        /           ______ |               /           ______                           
                                     /  349   9*\/ 1165       |       /  349   9*\/ 1165                                  |                                        /  349   9*\/ 1165       |                                       /  349   9*\/ 1165  |              /  349   9*\/ 1165                            
                                6*3 /   --- + ----------      |  6*3 /   --- + ----------                                 |                                   6*3 /   --- + ----------      |                                  6*3 /   --- + ---------- |         3*3 /   --- + ----------                           
                                  \/     2        2           \    \/     2        2                                      /                                     \/     2        2           \                                    \/     2        2      /           \/     2        2                                
$$\left(- \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{3} - \frac{19}{3 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} - \frac{2}{3}\right) + \left(\left(- \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}\right)\right) + \left(- \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6}\right)\right)\right)$$
=
       /                                         __________________\     /             __________________                            \
       |                                        /           ______ |     |            /           ______                             |
       |                                ___    /  349   9*\/ 1165  |     |    ___    /  349   9*\/ 1165                              |
       |                ___           \/ 3 *3 /   --- + ---------- |     |  \/ 3 *3 /   --- + ----------                  ___        |
       |           19*\/ 3                  \/     2        2      |     |        \/     2        2                  19*\/ 3         |
-2 + I*|- ------------------------- + -----------------------------| + I*|- ----------------------------- + -------------------------|
       |         __________________                 6              |     |                6                        __________________|
       |        /           ______                                 |     |                                        /           ______ |
       |       /  349   9*\/ 1165                                  |     |                                       /  349   9*\/ 1165  |
       |  6*3 /   --- + ----------                                 |     |                                  6*3 /   --- + ---------- |
       \    \/     2        2                                      /     \                                    \/     2        2      /
$$-2 + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}\right) + i \left(- \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6}\right)$$
producto
/           __________________                                 /                                         __________________\\ /           __________________                                 /             __________________                            \\ /                                       __________________\
|          /           ______                                  |                                        /           ______ || |          /           ______                                  |            /           ______                             || |                                      /           ______ |
|         /  349   9*\/ 1165                                   |                                ___    /  349   9*\/ 1165  || |         /  349   9*\/ 1165                                   |    ___    /  349   9*\/ 1165                              || |                                     /  349   9*\/ 1165  |
|      3 /   --- + ----------                                  |                ___           \/ 3 *3 /   --- + ---------- || |      3 /   --- + ----------                                  |  \/ 3 *3 /   --- + ----------                  ___        || |                                  3 /   --- + ---------- |
|  2   \/     2        2                     19                |           19*\/ 3                  \/     2        2      || |  2   \/     2        2                     19                |        \/     2        2                  19*\/ 3         || |  2               19              \/     2        2      |
|- - + ----------------------- + ------------------------- + I*|- ------------------------- + -----------------------------||*|- - + ----------------------- + ------------------------- + I*|- ----------------------------- + -------------------------||*|- - - ------------------------- - -----------------------|
|  3              6                     __________________     |         __________________                 6              || |  3              6                     __________________     |                6                        __________________|| |  3          __________________              3           |
|                                      /           ______      |        /           ______                                 || |                                      /           ______      |                                        /           ______ || |            /           ______                           |
|                                     /  349   9*\/ 1165       |       /  349   9*\/ 1165                                  || |                                     /  349   9*\/ 1165       |                                       /  349   9*\/ 1165  || |           /  349   9*\/ 1165                            |
|                                6*3 /   --- + ----------      |  6*3 /   --- + ----------                                 || |                                6*3 /   --- + ----------      |                                  6*3 /   --- + ---------- || |      3*3 /   --- + ----------                           |
\                                  \/     2        2           \    \/     2        2                                      // \                                  \/     2        2           \                                    \/     2        2      // \        \/     2        2                                /
$$\left(- \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6}\right)\right) \left(- \frac{2}{3} + \frac{19}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} + \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{6} + \frac{19 \sqrt{3}}{6 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}\right)\right) \left(- \frac{\sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}}{3} - \frac{19}{3 \sqrt[3]{\frac{9 \sqrt{1165}}{2} + \frac{349}{2}}} - \frac{2}{3}\right)$$
=
-9
$$-9$$
-9
Respuesta numérica [src]
x1 = 0.941979791567692 + 1.19578298592868*i
x2 = -3.88395958313538
x3 = 0.941979791567692 - 1.19578298592868*i
x3 = 0.941979791567692 - 1.19578298592868*i