Se da la desigualdad:
$$\left(\left(x^{3} + 6 x^{2}\right) + \frac{\left(28 x^{2} + 2 x\right) - 10}{x}\right) - 5 \leq 2$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\left(\left(x^{3} + 6 x^{2}\right) + \frac{\left(28 x^{2} + 2 x\right) - 10}{x}\right) - 5 = 2$$
Resolvemos:
$$x_{1} = - \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
$$x_{2} = - \frac{3}{2} + \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
$$x_{3} = - \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2} - \frac{3}{2} - \frac{\sqrt{- \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}} - \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}{2}$$
$$x_{4} = - \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2} - \frac{3}{2} + \frac{\sqrt{- \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}} - \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}{2}$$
Descartamos las soluciones complejas:
$$x_{1} = - \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
$$x_{2} = - \frac{3}{2} + \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
Las raíces dadas
$$x_{1} = - \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
$$x_{2} = - \frac{3}{2} + \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} \leq x_{1}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$\left(- \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}\right) + - \frac{1}{10}$$
=
$$- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
lo sustituimos en la expresión
$$\left(\left(x^{3} + 6 x^{2}\right) + \frac{\left(28 x^{2} + 2 x\right) - 10}{x}\right) - 5 \leq 2$$
$$-5 + \left(\frac{-10 + \left(2 \left(- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}\right) + 28 \left(- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}\right)^{2}\right)}{- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}} + \left(\left(- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}\right)^{3} + 6 \left(- \frac{8}{5} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}\right)^{2}\right)\right) \leq 2$$
2
/ _____________________________________________________________________________________________________________________________________________________________\
| / _______________________ |
| / / ___________ |
| / 58 / 62579 \/ 244609665 124 377 |
| / - -- - 2*3 / ----- + ------------- + ---------------------------------------------------------------------------------- - ------------------------------ |
| ________________________________________________________________________ / 3 \/ 432 144 ________________________________________________________________________ _______________________ |
| / _______________________ / / _______________________ / ___________ |
| / / ___________ / / / ___________ / 62579 \/ 244609665 |
| / 29 / 62579 \/ 244609665 377 / / 29 / 62579 \/ 244609665 377 9*3 / ----- + ------------- |
| / - -- + 2*3 / ----- + ------------- + ------------------------------ / / - -- + 2*3 / ----- + ------------- + ------------------------------ \/ 432 144 |
3 2 | / 3 \/ 432 144 _______________________ / / 3 \/ 432 144 _______________________ |
/ _____________________________________________________________________________________________________________________________________________________________\ / _____________________________________________________________________________________________________________________________________________________________\ ________________________________________________________________________ _____________________________________________________________________________________________________________________________________________________________ | / / ___________ / / / ___________ |
| / _______________________ | | / _______________________ | / _______________________ / _______________________ | / / 62579 \/ 244609665 / / / 62579 \/ 244609665 |
| / / ___________ | | / / ___________ | / / ___________ / / ___________ | / 9*3 / ----- + ------------- / / 9*3 / ----- + ------------- |
| / 58 / 62579 \/ 244609665 124 377 | | / 58 / 62579 \/ 244609665 124 377 | 66 / 29 / 62579 \/ 244609665 377 / 58 / 62579 \/ 244609665 124 377 | 8 \/ \/ 432 144 \/ \/ \/ 432 144 |
| / - -- - 2*3 / ----- + ------------- + ---------------------------------------------------------------------------------- - ------------------------------ | | / - -- - 2*3 / ----- + ------------- + ---------------------------------------------------------------------------------- - ------------------------------ | - -- + / - -- + 2*3 / ----- + ------------- + ------------------------------ - / - -- - 2*3 / ----- + ------------- + ---------------------------------------------------------------------------------- - ------------------------------ + 28*|- - + ---------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------|
| ________________________________________________________________________ / 3 \/ 432 144 ________________________________________________________________________ _______________________ | | ________________________________________________________________________ / 3 \/ 432 144 ________________________________________________________________________ _______________________ | 5 / 3 \/ 432 144 _______________________ / 3 \/ 432 144 ________________________________________________________________________ _______________________ \ 5 2 2 /
| / _______________________ / / _______________________ / ___________ | | / _______________________ / / _______________________ / ___________ | / / ___________ / / _______________________ / ___________
| / / ___________ / / / ___________ / 62579 \/ 244609665 | | / / ___________ / / / ___________ / 62579 \/ 244609665 | / / 62579 \/ 244609665 / / / ___________ / 62579 \/ 244609665
| / 29 / 62579 \/ 244609665 377 / / 29 / 62579 \/ 244609665 377 9*3 / ----- + ------------- | | / 29 / 62579 \/ 244609665 377 / / 29 / 62579 \/ 244609665 377 9*3 / ----- + ------------- | / 9*3 / ----- + ------------- / / 29 / 62579 \/ 244609665 377 9*3 / ----- + -------------
| / - -- + 2*3 / ----- + ------------- + ------------------------------ / / - -- + 2*3 / ----- + ------------- + ------------------------------ \/ 432 144 | | / - -- + 2*3 / ----- + ------------- + ------------------------------ / / - -- + 2*3 / ----- + ------------- + ------------------------------ \/ 432 144 | \/ \/ 432 144 / / - -- + 2*3 / ----- + ------------- + ------------------------------ \/ 432 144
| / 3 \/ 432 144 _______________________ / / 3 \/ 432 144 _______________________ | | / 3 \/ 432 144 _______________________ / / 3 \/ 432 144 _______________________ | / / 3 \/ 432 144 _______________________ <= 2
| / / ___________ / / / ___________ | | / / ___________ / / / ___________ | / / / ___________
| / / 62579 \/ 244609665 / / / 62579 \/ 244609665 | | / / 62579 \/ 244609665 / / / 62579 \/ 244609665 | / / / 62579 \/ 244609665
| / 9*3 / ----- + ------------- / / 9*3 / ----- + ------------- | | / 9*3 / ----- + ------------- / / 9*3 / ----- + ------------- | / / 9*3 / ----- + -------------
| 8 \/ \/ 432 144 \/ \/ \/ 432 144 | | 8 \/ \/ 432 144 \/ \/ \/ 432 144 | \/ \/ \/ 432 144
-5 + |- - + ---------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------| + 6*|- - + ---------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------| + --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\ 5 2 2 / \ 5 2 2 / _____________________________________________________________________________________________________________________________________________________________
/ _______________________
/ / ___________
/ 58 / 62579 \/ 244609665 124 377
/ - -- - 2*3 / ----- + ------------- + ---------------------------------------------------------------------------------- - ------------------------------
________________________________________________________________________ / 3 \/ 432 144 ________________________________________________________________________ _______________________
/ _______________________ / / _______________________ / ___________
/ / ___________ / / / ___________ / 62579 \/ 244609665
/ 29 / 62579 \/ 244609665 377 / / 29 / 62579 \/ 244609665 377 9*3 / ----- + -------------
/ - -- + 2*3 / ----- + ------------- + ------------------------------ / / - -- + 2*3 / ----- + ------------- + ------------------------------ \/ 432 144
/ 3 \/ 432 144 _______________________ / / 3 \/ 432 144 _______________________
/ / ___________ / / / ___________
/ / 62579 \/ 244609665 / / / 62579 \/ 244609665
/ 9*3 / ----- + ------------- / / 9*3 / ----- + -------------
8 \/ \/ 432 144 \/ \/ \/ 432 144
- - + ---------------------------------------------------------------------------------- - ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
5 2 2
significa que una de las soluciones de nuestra ecuación será con:
$$x \leq - \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
_____ _____
\ /
-------•-------•-------
x1 x2
Recibiremos otras soluciones de la desigualdad pasando al polo siguiente etc.
etc.
Respuesta:
$$x \leq - \frac{3}{2} - \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$
$$x \geq - \frac{3}{2} + \frac{\sqrt{- \frac{58}{3} - 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}} - \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + \frac{124}{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}}}{2} + \frac{\sqrt{- \frac{29}{3} + \frac{377}{9 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}} + 2 \sqrt[3]{\frac{\sqrt{244609665}}{144} + \frac{62579}{432}}}}{2}$$