Se da la desigualdad:
$$\sqrt{x} - \frac{2}{\sqrt{x - 2}} \leq 3$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\sqrt{x} - \frac{2}{\sqrt{x - 2}} = 3$$
Resolvemos:
$$x_{1} = \frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{11}{2}$$
$$x_{1} = \frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{11}{2}$$
Las raíces dadas
$$x_{1} = \frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{11}{2}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \left(\frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{11}{2}\right)$$
=
$$\frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{27}{5}$$
lo sustituimos en la expresión
$$\sqrt{x} - \frac{2}{\sqrt{x - 2}} \leq 3$$
$$- \frac{2}{\sqrt{-2 + \left(\frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{27}{5}\right)}} + \sqrt{\frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{27}{5}} \leq 3$$
___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________
/ __________________________________________________________________________________________________________________________________________________
/ / ______________________
/ / 130 / 35119 ______ 288 1823
/ / --- - 2*3 / - ----- + 8*\/ 2442 + --------------------------------------------------------------------------- + -----------------------------
/ ___________________________________________________________________ / 3 \/ 216 ___________________________________________________________________ ______________________
/ / ______________________ / / ______________________ / 35119 ______
/ / 65 / 35119 ______ 1823 / / 65 / 35119 ______ 1823 18*3 / - ----- + 8*\/ 2442
/ / -- + 2*3 / - ----- + 8*\/ 2442 - ----------------------------- / / -- + 2*3 / - ----- + 8*\/ 2442 - ----------------------------- \/ 216
/ / 3 \/ 216 ______________________ / / 3 \/ 216 ______________________
/ / / 35119 ______ / / / 35119 ______
/ / 18*3 / - ----- + 8*\/ 2442 / / 18*3 / - ----- + 8*\/ 2442
/ 27 \/ \/ 216 \/ \/ \/ 216 2
/ -- + --------------------------------------------------------------------------- + -------------------------------------------------------------------------------------------------------------------------------------------------------------- - ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
\/ 5 2 2 ___________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________ <= 3
/ __________________________________________________________________________________________________________________________________________________
/ / ______________________
/ / 130 / 35119 ______ 288 1823
/ / --- - 2*3 / - ----- + 8*\/ 2442 + --------------------------------------------------------------------------- + -----------------------------
/ ___________________________________________________________________ / 3 \/ 216 ___________________________________________________________________ ______________________
/ / ______________________ / / ______________________ / 35119 ______
/ / 65 / 35119 ______ 1823 / / 65 / 35119 ______ 1823 18*3 / - ----- + 8*\/ 2442
/ / -- + 2*3 / - ----- + 8*\/ 2442 - ----------------------------- / / -- + 2*3 / - ----- + 8*\/ 2442 - ----------------------------- \/ 216
/ / 3 \/ 216 ______________________ / / 3 \/ 216 ______________________
/ / / 35119 ______ / / / 35119 ______
/ / 18*3 / - ----- + 8*\/ 2442 / / 18*3 / - ----- + 8*\/ 2442
/ 17 \/ \/ 216 \/ \/ \/ 216
/ -- + --------------------------------------------------------------------------- + --------------------------------------------------------------------------------------------------------------------------------------------------------------
\/ 5 2 2
significa que la solución de la desigualdad será con:
$$x \leq \frac{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}{2} + \frac{\sqrt{- 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + \frac{130}{3} + \frac{288}{\sqrt{- \frac{1823}{18 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}}} + 2 \sqrt[3]{- \frac{35119}{216} + 8 \sqrt{2442}} + \frac{65}{3}}}}}{2} + \frac{11}{2}$$
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