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-x^3+4*x^2-15*x+30=0 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
   3      2                
- x  + 4*x  - 15*x + 30 = 0
$$\left(- 15 x + \left(- x^{3} + 4 x^{2}\right)\right) + 30 = 0$$
Teorema de Cardano-Vieta
reescribamos la ecuación
$$\left(- 15 x + \left(- x^{3} + 4 x^{2}\right)\right) + 30 = 0$$
de
$$a x^{3} + b x^{2} + c x + d = 0$$
como ecuación cúbica reducida
$$x^{3} + \frac{b x^{2}}{a} + \frac{c x}{a} + \frac{d}{a} = 0$$
$$x^{3} - 4 x^{2} + 15 x - 30 = 0$$
$$p x^{2} + q x + v + x^{3} = 0$$
donde
$$p = \frac{b}{a}$$
$$p = -4$$
$$q = \frac{c}{a}$$
$$q = 15$$
$$v = \frac{d}{a}$$
$$v = -30$$
Fórmulas de Cardano-Vieta
$$x_{1} + x_{2} + x_{3} = - p$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = q$$
$$x_{1} x_{2} x_{3} = v$$
$$x_{1} + x_{2} + x_{3} = 4$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = 15$$
$$x_{1} x_{2} x_{3} = -30$$
Gráfica
Respuesta rápida [src]
              _______________                               /                                       _______________\
             /         _____                                |                                      /         _____ |
            /  199   \/ 790                                 |                              ___    /  199   \/ 790  |
         3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- |
     4   \/     27      3                  29               |          29*\/ 3                 \/     27      3    |
x1 = - - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------|
     3            2                     _______________     |          _______________               2             |
                                       /         _____      |         /         _____                              |
                                      /  199   \/ 790       |        /  199   \/ 790                               |
                                18*3 /   --- + -------      |  18*3 /   --- + -------                              |
                                   \/     27      3         \     \/     27      3                                 /
$$x_{1} = - \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} - \frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}\right)$$
              _______________                               /           _______________                          \
             /         _____                                |          /         _____                           |
            /  199   \/ 790                                 |  ___    /  199   \/ 790                            |
         3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       |
     4   \/     27      3                  29               |      \/     27      3               29*\/ 3        |
x2 = - - -------------------- + ----------------------- + I*|-------------------------- + -----------------------|
     3            2                     _______________     |            2                        _______________|
                                       /         _____      |                                    /         _____ |
                                      /  199   \/ 790       |                                   /  199   \/ 790  |
                                18*3 /   --- + -------      |                             18*3 /   --- + ------- |
                                   \/     27      3         \                                \/     27      3    /
$$x_{2} = - \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(\frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2}\right)$$
              _______________                         
             /         _____                          
     4      /  199   \/ 790               29          
x3 = - + 3 /   --- + -------  - ----------------------
     3   \/     27      3              _______________
                                      /         _____ 
                                     /  199   \/ 790  
                                9*3 /   --- + ------- 
                                  \/     27      3    
$$x_{3} = - \frac{29}{9 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}$$
x3 = -29/(9*(199/27 + sqrt(790)/3)^(1/3)) + 4/3 + (199/27 + sqrt(790)/3)^(1/3)
Suma y producto de raíces [src]
suma
         _______________                               /                                       _______________\            _______________                               /           _______________                          \                                                    
        /         _____                                |                                      /         _____ |           /         _____                                |          /         _____                           |                                                    
       /  199   \/ 790                                 |                              ___    /  199   \/ 790  |          /  199   \/ 790                                 |  ___    /  199   \/ 790                            |            _______________                         
    3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- |       3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       |           /         _____                          
4   \/     27      3                  29               |          29*\/ 3                 \/     27      3    |   4   \/     27      3                  29               |      \/     27      3               29*\/ 3        |   4      /  199   \/ 790               29          
- - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------| + - - -------------------- + ----------------------- + I*|-------------------------- + -----------------------| + - + 3 /   --- + -------  - ----------------------
3            2                     _______________     |          _______________               2             |   3            2                     _______________     |            2                        _______________|   3   \/     27      3              _______________
                                  /         _____      |         /         _____                              |                                     /         _____      |                                    /         _____ |                                    /         _____ 
                                 /  199   \/ 790       |        /  199   \/ 790                               |                                    /  199   \/ 790       |                                   /  199   \/ 790  |                                   /  199   \/ 790  
                           18*3 /   --- + -------      |  18*3 /   --- + -------                              |                              18*3 /   --- + -------      |                             18*3 /   --- + ------- |                              9*3 /   --- + ------- 
                              \/     27      3         \     \/     27      3                                 /                                 \/     27      3         \                                \/     27      3    /                                \/     27      3    
$$\left(- \frac{29}{9 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}\right) + \left(\left(- \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} - \frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}\right)\right) + \left(- \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(\frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2}\right)\right)\right)$$
=
      /           _______________                          \     /                                       _______________\
      |          /         _____                           |     |                                      /         _____ |
      |  ___    /  199   \/ 790                            |     |                              ___    /  199   \/ 790  |
      |\/ 3 *3 /   --- + -------                 ___       |     |               ___          \/ 3 *3 /   --- + ------- |
      |      \/     27      3               29*\/ 3        |     |          29*\/ 3                 \/     27      3    |
4 + I*|-------------------------- + -----------------------| + I*|- ----------------------- - --------------------------|
      |            2                        _______________|     |          _______________               2             |
      |                                    /         _____ |     |         /         _____                              |
      |                                   /  199   \/ 790  |     |        /  199   \/ 790                               |
      |                             18*3 /   --- + ------- |     |  18*3 /   --- + -------                              |
      \                                \/     27      3    /     \     \/     27      3                                 /
$$4 + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} - \frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}\right) + i \left(\frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2}\right)$$
producto
/         _______________                               /                                       _______________\\ /         _______________                               /           _______________                          \\                                                    
|        /         _____                                |                                      /         _____ || |        /         _____                                |          /         _____                           ||                                                    
|       /  199   \/ 790                                 |                              ___    /  199   \/ 790  || |       /  199   \/ 790                                 |  ___    /  199   \/ 790                            || /         _______________                         \
|    3 /   --- + -------                                |               ___          \/ 3 *3 /   --- + ------- || |    3 /   --- + -------                                |\/ 3 *3 /   --- + -------                 ___       || |        /         _____                          |
|4   \/     27      3                  29               |          29*\/ 3                 \/     27      3    || |4   \/     27      3                  29               |      \/     27      3               29*\/ 3        || |4      /  199   \/ 790               29          |
|- - -------------------- + ----------------------- + I*|- ----------------------- - --------------------------||*|- - -------------------- + ----------------------- + I*|-------------------------- + -----------------------||*|- + 3 /   --- + -------  - ----------------------|
|3            2                     _______________     |          _______________               2             || |3            2                     _______________     |            2                        _______________|| |3   \/     27      3              _______________|
|                                  /         _____      |         /         _____                              || |                                  /         _____      |                                    /         _____ || |                                 /         _____ |
|                                 /  199   \/ 790       |        /  199   \/ 790                               || |                                 /  199   \/ 790       |                                   /  199   \/ 790  || |                                /  199   \/ 790  |
|                           18*3 /   --- + -------      |  18*3 /   --- + -------                              || |                           18*3 /   --- + -------      |                             18*3 /   --- + ------- || |                           9*3 /   --- + ------- |
\                              \/     27      3         \     \/     27      3                                 // \                              \/     27      3         \                                \/     27      3    // \                             \/     27      3    /
$$\left(- \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(\frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2}\right)\right) \left(- \frac{\sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} + \frac{29}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + i \left(- \frac{\sqrt{3} \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}{2} - \frac{29 \sqrt{3}}{18 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}}\right)\right) \left(- \frac{29}{9 \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}} + \frac{4}{3} + \sqrt[3]{\frac{199}{27} + \frac{\sqrt{790}}{3}}\right)$$
=
30
$$30$$
30
Respuesta numérica [src]
x1 = 2.63177698620825
x2 = 0.684111506895875 + 3.3062264904926*i
x3 = 0.684111506895875 - 3.3062264904926*i
x3 = 0.684111506895875 - 3.3062264904926*i