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-1*x^3+5*x^2-12*x+15=0 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
   3      2                
- x  + 5*x  - 12*x + 15 = 0
$$\left(- 12 x + \left(- x^{3} + 5 x^{2}\right)\right) + 15 = 0$$
Teorema de Cardano-Vieta
reescribamos la ecuación
$$\left(- 12 x + \left(- x^{3} + 5 x^{2}\right)\right) + 15 = 0$$
de
$$a x^{3} + b x^{2} + c x + d = 0$$
como ecuación cúbica reducida
$$x^{3} + \frac{b x^{2}}{a} + \frac{c x}{a} + \frac{d}{a} = 0$$
$$x^{3} - 5 x^{2} + 12 x - 15 = 0$$
$$p x^{2} + q x + v + x^{3} = 0$$
donde
$$p = \frac{b}{a}$$
$$p = -5$$
$$q = \frac{c}{a}$$
$$q = 12$$
$$v = \frac{d}{a}$$
$$v = -15$$
Fórmulas de Cardano-Vieta
$$x_{1} + x_{2} + x_{3} = - p$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = q$$
$$x_{1} x_{2} x_{3} = v$$
$$x_{1} + x_{2} + x_{3} = 5$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = 12$$
$$x_{1} x_{2} x_{3} = -15$$
Gráfica
Respuesta rápida [src]
              _______________                               /                                       _______________\
             /         _____                                |                                      /         _____ |
            /  115   \/ 229                                 |                              ___    /  115   \/ 229  |
         3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- |
     5   \/     54      6                  11               |          11*\/ 3                 \/     54      6    |
x1 = - - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------|
     3            2                     _______________     |          _______________               2             |
                                       /         _____      |         /         _____                              |
                                      /  115   \/ 229       |        /  115   \/ 229                               |
                                18*3 /   --- + -------      |  18*3 /   --- + -------                              |
                                   \/     54      6         \     \/     54      6                                 /
$$x_{1} = - \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} - \frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}\right)$$
              _______________                               /           _______________                          \
             /         _____                                |          /         _____                           |
            /  115   \/ 229                                 |  ___    /  115   \/ 229                            |
         3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       |
     5   \/     54      6                  11               |      \/     54      6               11*\/ 3        |
x2 = - - -------------------- + ----------------------- + I*|-------------------------- + -----------------------|
     3            2                     _______________     |            2                        _______________|
                                       /         _____      |                                    /         _____ |
                                      /  115   \/ 229       |                                   /  115   \/ 229  |
                                18*3 /   --- + -------      |                             18*3 /   --- + ------- |
                                   \/     54      6         \                                \/     54      6    /
$$x_{2} = - \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(\frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2}\right)$$
              _______________                         
             /         _____                          
     5      /  115   \/ 229               11          
x3 = - + 3 /   --- + -------  - ----------------------
     3   \/     54      6              _______________
                                      /         _____ 
                                     /  115   \/ 229  
                                9*3 /   --- + ------- 
                                  \/     54      6    
$$x_{3} = - \frac{11}{9 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}$$
x3 = -11/(9*(115/54 + sqrt(229)/6)^(1/3)) + 5/3 + (115/54 + sqrt(229)/6)^(1/3)
Suma y producto de raíces [src]
suma
         _______________                               /                                       _______________\            _______________                               /           _______________                          \                                                    
        /         _____                                |                                      /         _____ |           /         _____                                |          /         _____                           |                                                    
       /  115   \/ 229                                 |                              ___    /  115   \/ 229  |          /  115   \/ 229                                 |  ___    /  115   \/ 229                            |            _______________                         
    3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- |       3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       |           /         _____                          
5   \/     54      6                  11               |          11*\/ 3                 \/     54      6    |   5   \/     54      6                  11               |      \/     54      6               11*\/ 3        |   5      /  115   \/ 229               11          
- - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------| + - - -------------------- + ----------------------- + I*|-------------------------- + -----------------------| + - + 3 /   --- + -------  - ----------------------
3            2                     _______________     |          _______________               2             |   3            2                     _______________     |            2                        _______________|   3   \/     54      6              _______________
                                  /         _____      |         /         _____                              |                                     /         _____      |                                    /         _____ |                                    /         _____ 
                                 /  115   \/ 229       |        /  115   \/ 229                               |                                    /  115   \/ 229       |                                   /  115   \/ 229  |                                   /  115   \/ 229  
                           18*3 /   --- + -------      |  18*3 /   --- + -------                              |                              18*3 /   --- + -------      |                             18*3 /   --- + ------- |                              9*3 /   --- + ------- 
                              \/     54      6         \     \/     54      6                                 /                                 \/     54      6         \                                \/     54      6    /                                \/     54      6    
$$\left(- \frac{11}{9 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}\right) + \left(\left(- \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} - \frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}\right)\right) + \left(- \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(\frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2}\right)\right)\right)$$
=
      /           _______________                          \     /                                       _______________\
      |          /         _____                           |     |                                      /         _____ |
      |  ___    /  115   \/ 229                            |     |                              ___    /  115   \/ 229  |
      |\/ 3 *3 /   --- + -------                 ___       |     |               ___          \/ 3 *3 /   --- + ------- |
      |      \/     54      6               11*\/ 3        |     |          11*\/ 3                 \/     54      6    |
5 + I*|-------------------------- + -----------------------| + I*|- ----------------------- - --------------------------|
      |            2                        _______________|     |          _______________               2             |
      |                                    /         _____ |     |         /         _____                              |
      |                                   /  115   \/ 229  |     |        /  115   \/ 229                               |
      |                             18*3 /   --- + ------- |     |  18*3 /   --- + -------                              |
      \                                \/     54      6    /     \     \/     54      6                                 /
$$5 + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} - \frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}\right) + i \left(\frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2}\right)$$
producto
/         _______________                               /                                       _______________\\ /         _______________                               /           _______________                          \\                                                    
|        /         _____                                |                                      /         _____ || |        /         _____                                |          /         _____                           ||                                                    
|       /  115   \/ 229                                 |                              ___    /  115   \/ 229  || |       /  115   \/ 229                                 |  ___    /  115   \/ 229                            || /         _______________                         \
|    3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- || |    3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       || |        /         _____                          |
|5   \/     54      6                  11               |          11*\/ 3                 \/     54      6    || |5   \/     54      6                  11               |      \/     54      6               11*\/ 3        || |5      /  115   \/ 229               11          |
|- - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------||*|- - -------------------- + ----------------------- + I*|-------------------------- + -----------------------||*|- + 3 /   --- + -------  - ----------------------|
|3            2                     _______________     |          _______________               2             || |3            2                     _______________     |            2                        _______________|| |3   \/     54      6              _______________|
|                                  /         _____      |         /         _____                              || |                                  /         _____      |                                    /         _____ || |                                 /         _____ |
|                                 /  115   \/ 229       |        /  115   \/ 229                               || |                                 /  115   \/ 229       |                                   /  115   \/ 229  || |                                /  115   \/ 229  |
|                           18*3 /   --- + -------      |  18*3 /   --- + -------                              || |                           18*3 /   --- + -------      |                             18*3 /   --- + ------- || |                           9*3 /   --- + ------- |
\                              \/     54      6         \     \/     54      6                                 // \                              \/     54      6         \                                \/     54      6    // \                             \/     54      6    /
$$\left(- \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(\frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2}\right)\right) \left(- \frac{\sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} + \frac{11}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}{2} - \frac{11 \sqrt{3}}{18 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}}\right)\right) \left(- \frac{11}{9 \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}} + \frac{5}{3} + \sqrt[3]{\frac{115}{54} + \frac{\sqrt{229}}{6}}\right)$$
=
15
$$15$$
15
Respuesta numérica [src]
x1 = 1.1980924212362 + 2.07974809462801*i
x2 = 1.1980924212362 - 2.07974809462801*i
x3 = 2.60381515752759
x3 = 2.60381515752759