Se da la desigualdad:
$$\left(x + \frac{\left(x - 4\right) \left(x + 1\right)}{x^{2}}\right) - 6 > 0$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\left(x + \frac{\left(x - 4\right) \left(x + 1\right)}{x^{2}}\right) - 6 = 0$$
Resolvemos:
$$x_{1} = \frac{5}{3} + \left(- \frac{1}{2} - \frac{\sqrt{3} i}{2}\right) \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}} + \frac{34}{9 \left(- \frac{1}{2} - \frac{\sqrt{3} i}{2}\right) \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}}$$
$$x_{2} = \frac{5}{3} + \frac{34}{9 \left(- \frac{1}{2} + \frac{\sqrt{3} i}{2}\right) \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \left(- \frac{1}{2} + \frac{\sqrt{3} i}{2}\right) \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
$$x_{3} = \frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
Descartamos las soluciones complejas:
$$x_{1} = \frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
Las raíces dadas
$$x_{1} = \frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} < x_{1}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \left(\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}\right)$$
=
$$\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{47}{30} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
lo sustituimos en la expresión
$$\left(x + \frac{\left(x - 4\right) \left(x + 1\right)}{x^{2}}\right) - 6 > 0$$
$$-6 + \left(\frac{\left(-4 + \left(\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{47}{30} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}\right)\right) \left(1 + \left(\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{47}{30} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}\right)\right)}{\left(\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{47}{30} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}\right)^{2}} + \left(\frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{47}{30} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}\right)\right) > 0$$
/ _________________ \ / _________________ \
| / ____ | | / ____ |
| 73 / 493 17*\/ 33 34 | |77 / 493 17*\/ 33 34 |
|- -- + 3 / --- + --------- + ------------------------|*|-- + 3 / --- + --------- + ------------------------|
| 30 \/ 54 18 _________________| |30 \/ 54 18 _________________|
| / ____ | | / ____ |
_________________ | / 493 17*\/ 33 | | / 493 17*\/ 33 |
/ ____ | 9*3 / --- + --------- | | 9*3 / --- + --------- |
133 / 493 17*\/ 33 34 \ \/ 54 18 / \ \/ 54 18 /
- --- + 3 / --- + --------- + ------------------------ + -------------------------------------------------------------------------------------------------------------------
30 \/ 54 18 _________________ 2 > 0
/ ____ / _________________ \
/ 493 17*\/ 33 | / ____ |
9*3 / --- + --------- |47 / 493 17*\/ 33 34 |
\/ 54 18 |-- + 3 / --- + --------- + ------------------------|
|30 \/ 54 18 _________________|
| / ____ |
| / 493 17*\/ 33 |
| 9*3 / --- + --------- |
\ \/ 54 18 /
Entonces
$$x < \frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
no se cumple
significa que la solución de la desigualdad será con:
$$x > \frac{34}{9 \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}} + \frac{5}{3} + \sqrt[3]{\frac{17 \sqrt{33}}{18} + \frac{493}{54}}$$
_____
/
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