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-4x^3=5x+64 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
    3           
-4*x  = 5*x + 64
$$- 4 x^{3} = 5 x + 64$$
Teorema de Cardano-Vieta
reescribamos la ecuación
$$- 4 x^{3} = 5 x + 64$$
de
$$a x^{3} + b x^{2} + c x + d = 0$$
como ecuación cúbica reducida
$$x^{3} + \frac{b x^{2}}{a} + \frac{c x}{a} + \frac{d}{a} = 0$$
$$x^{3} + \frac{5 x}{4} + 16 = 0$$
$$p x^{2} + q x + v + x^{3} = 0$$
donde
$$p = \frac{b}{a}$$
$$p = 0$$
$$q = \frac{c}{a}$$
$$q = \frac{5}{4}$$
$$v = \frac{d}{a}$$
$$v = 16$$
Fórmulas de Cardano-Vieta
$$x_{1} + x_{2} + x_{3} = - p$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = q$$
$$x_{1} x_{2} x_{3} = v$$
$$x_{1} + x_{2} + x_{3} = 0$$
$$x_{1} x_{2} + x_{1} x_{3} + x_{2} x_{3} = \frac{5}{4}$$
$$x_{1} x_{2} x_{3} = 16$$
Gráfica
Suma y producto de raíces [src]
suma
                                     ____________________     /           ____________________                              \                                        ____________________     /                                           ____________________\          ____________________                              
                                    /           ________      |          /           ________                               |                                       /           ________      |                                          /           ________ |         /           ________                               
                                   /        3*\/ 332151       |  ___    /        3*\/ 332151                                |                                      /        3*\/ 332151       |                                  ___    /        3*\/ 332151  |        /        3*\/ 332151                                
                                3 /   216 + ------------      |\/ 3 *3 /   216 + ------------                  ___          |                                   3 /   216 + ------------      |                ___             \/ 3 *3 /   216 + ------------ |     3 /   216 + ------------                               
               5                \/               8            |      \/               8                    5*\/ 3           |                  5                \/               8            |            5*\/ 3                    \/               8       |     \/               8                       5             
- --------------------------- + ------------------------- + I*|------------------------------- + ---------------------------| + - --------------------------- + ------------------------- + I*|- --------------------------- - -------------------------------| + - ------------------------- + ---------------------------
         ____________________               6                 |               6                         ____________________|            ____________________               6                 |         ____________________                  6               |                 3                      ____________________
        /           ________                                  |                                        /           ________ |           /           ________                                  |        /           ________                                   |                                       /           ________ 
       /        3*\/ 332151                                   |                                       /        3*\/ 332151  |          /        3*\/ 332151                                   |       /        3*\/ 332151                                    |                                      /        3*\/ 332151  
  8*3 /   216 + ------------                                  |                                  8*3 /   216 + ------------ |     8*3 /   216 + ------------                                  |  8*3 /   216 + ------------                                   |                                 4*3 /   216 + ------------ 
    \/               8                                        \                                    \/               8       /       \/               8                                        \    \/               8                                         /                                   \/               8       
$$\left(- \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{3} + \frac{5}{4 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right) + \left(\left(- \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} - \frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right)\right) + \left(- \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(\frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6}\right)\right)\right)$$
=
  /                                           ____________________\     /           ____________________                              \
  |                                          /           ________ |     |          /           ________                               |
  |                                  ___    /        3*\/ 332151  |     |  ___    /        3*\/ 332151                                |
  |                ___             \/ 3 *3 /   216 + ------------ |     |\/ 3 *3 /   216 + ------------                  ___          |
  |            5*\/ 3                    \/               8       |     |      \/               8                    5*\/ 3           |
I*|- --------------------------- - -------------------------------| + I*|------------------------------- + ---------------------------|
  |         ____________________                  6               |     |               6                         ____________________|
  |        /           ________                                   |     |                                        /           ________ |
  |       /        3*\/ 332151                                    |     |                                       /        3*\/ 332151  |
  |  8*3 /   216 + ------------                                   |     |                                  8*3 /   216 + ------------ |
  \    \/               8                                         /     \                                    \/               8       /
$$i \left(- \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} - \frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right) + i \left(\frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6}\right)$$
producto
/                                     ____________________     /           ____________________                              \\ /                                     ____________________     /                                           ____________________\\ /       ____________________                              \
|                                    /           ________      |          /           ________                               || |                                    /           ________      |                                          /           ________ || |      /           ________                               |
|                                   /        3*\/ 332151       |  ___    /        3*\/ 332151                                || |                                   /        3*\/ 332151       |                                  ___    /        3*\/ 332151  || |     /        3*\/ 332151                                |
|                                3 /   216 + ------------      |\/ 3 *3 /   216 + ------------                  ___          || |                                3 /   216 + ------------      |                ___             \/ 3 *3 /   216 + ------------ || |  3 /   216 + ------------                               |
|               5                \/               8            |      \/               8                    5*\/ 3           || |               5                \/               8            |            5*\/ 3                    \/               8       || |  \/               8                       5             |
|- --------------------------- + ------------------------- + I*|------------------------------- + ---------------------------||*|- --------------------------- + ------------------------- + I*|- --------------------------- - -------------------------------||*|- ------------------------- + ---------------------------|
|         ____________________               6                 |               6                         ____________________|| |         ____________________               6                 |         ____________________                  6               || |              3                      ____________________|
|        /           ________                                  |                                        /           ________ || |        /           ________                                  |        /           ________                                   || |                                    /           ________ |
|       /        3*\/ 332151                                   |                                       /        3*\/ 332151  || |       /        3*\/ 332151                                   |       /        3*\/ 332151                                    || |                                   /        3*\/ 332151  |
|  8*3 /   216 + ------------                                  |                                  8*3 /   216 + ------------ || |  8*3 /   216 + ------------                                  |  8*3 /   216 + ------------                                   || |                              4*3 /   216 + ------------ |
\    \/               8                                        \                                    \/               8       // \    \/               8                                        \    \/               8                                         // \                                \/               8       /
$$\left(- \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(\frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6}\right)\right) \left(- \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} - \frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right)\right) \left(- \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{3} + \frac{5}{4 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right)$$
=
-16
$$-16$$
-16
Respuesta rápida [src]
                                          ____________________     /           ____________________                              \
                                         /           ________      |          /           ________                               |
                                        /        3*\/ 332151       |  ___    /        3*\/ 332151                                |
                                     3 /   216 + ------------      |\/ 3 *3 /   216 + ------------                  ___          |
                    5                \/               8            |      \/               8                    5*\/ 3           |
x1 = - --------------------------- + ------------------------- + I*|------------------------------- + ---------------------------|
              ____________________               6                 |               6                         ____________________|
             /           ________                                  |                                        /           ________ |
            /        3*\/ 332151                                   |                                       /        3*\/ 332151  |
       8*3 /   216 + ------------                                  |                                  8*3 /   216 + ------------ |
         \/               8                                        \                                    \/               8       /
$$x_{1} = - \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(\frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6}\right)$$
                                          ____________________     /                                           ____________________\
                                         /           ________      |                                          /           ________ |
                                        /        3*\/ 332151       |                                  ___    /        3*\/ 332151  |
                                     3 /   216 + ------------      |                ___             \/ 3 *3 /   216 + ------------ |
                    5                \/               8            |            5*\/ 3                    \/               8       |
x2 = - --------------------------- + ------------------------- + I*|- --------------------------- - -------------------------------|
              ____________________               6                 |         ____________________                  6               |
             /           ________                                  |        /           ________                                   |
            /        3*\/ 332151                                   |       /        3*\/ 332151                                    |
       8*3 /   216 + ------------                                  |  8*3 /   216 + ------------                                   |
         \/               8                                        \    \/               8                                         /
$$x_{2} = - \frac{5}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}} + \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} + i \left(- \frac{\sqrt{3} \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{6} - \frac{5 \sqrt{3}}{8 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}\right)$$
            ____________________                              
           /           ________                               
          /        3*\/ 332151                                
       3 /   216 + ------------                               
       \/               8                       5             
x3 = - ------------------------- + ---------------------------
                   3                      ____________________
                                         /           ________ 
                                        /        3*\/ 332151  
                                   4*3 /   216 + ------------ 
                                     \/               8       
$$x_{3} = - \frac{\sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}{3} + \frac{5}{4 \sqrt[3]{216 + \frac{3 \sqrt{332151}}{8}}}$$
x3 = -(216 + 3*sqrt(332151)/8)^(1/3)/3 + 5/(4*(216 + 3*sqrt(332151)/8)^(1/3))
Respuesta numérica [src]
x1 = 1.177370322821 - 2.32564026263282*i
x2 = 1.177370322821 + 2.32564026263282*i
x3 = -2.354740645642
x3 = -2.354740645642