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(16^x-2×4^x+1)²-23(16^x-2×4^x+1)-112>0 desigualdades

En la desigualdad la incógnita

Solución

Ha introducido [src]
                2                                
/  x      x    \       /  x      x    \          
\16  - 2*4  + 1/  - 23*\16  - 2*4  + 1/ - 112 > 0
$$\left(\left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)^{2} - 23 \left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)\right) - 112 > 0$$
(16^x - 2*4^x + 1)^2 - 23*(16^x - 2*4^x + 1) - 112 > 0
Solución detallada
Se da la desigualdad:
$$\left(\left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)^{2} - 23 \left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)\right) - 112 > 0$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\left(\left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)^{2} - 23 \left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)\right) - 112 = 0$$
Resolvemos:
$$x_{1} = \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
$$x_{2} = \frac{\log{\left(-1 + \frac{\sqrt{2} \sqrt{23 + \sqrt{977}}}{2} \right)} + i \pi}{2 \log{\left(2 \right)}}$$
$$x_{3} = \frac{\frac{\log{\left(1 + \frac{\sqrt{2} \sqrt{23 + \sqrt{977}}}{2} \right)}}{2} + i \pi}{\log{\left(2 \right)}}$$
$$x_{4} = - \frac{\log{\left(- \frac{2}{21 - \sqrt{977}} \right)} + 2 i \operatorname{atan}{\left(\frac{\sqrt{2} \sqrt{-23 + \sqrt{977}}}{2} \right)}}{4 \log{\left(2 \right)}}$$
$$x_{5} = - \frac{\log{\left(- \frac{2}{- \sqrt{2} \sqrt{23 + \sqrt{977}} + 2} \right)} + i \pi}{2 \log{\left(2 \right)}}$$
$$x_{6} = \frac{- \log{\left(2 \right)} + \log{\left(-21 + \sqrt{977} \right)} + 2 i \operatorname{atan}{\left(\frac{\sqrt{2} \sqrt{-23 + \sqrt{977}}}{2} \right)}}{4 \log{\left(2 \right)}}$$
$$x_{7} = \frac{- \log{\left(2 \right)} + \log{\left(-21 + \sqrt{977} \right)} + 4 \log{\left(- e^{\frac{i \operatorname{atan}{\left(\frac{\sqrt{2} \sqrt{-23 + \sqrt{977}}}{2} \right)}}{2}} \right)}}{4 \log{\left(2 \right)}}$$
$$x_{8} = \frac{- \frac{\log{\left(2 \right)}}{4} + \frac{\log{\left(-21 + \sqrt{977} \right)}}{4} + \log{\left(- e^{- \frac{i \operatorname{atan}{\left(\frac{\sqrt{2} \sqrt{-23 + \sqrt{977}}}{2} \right)}}{2}} \right)}}{\log{\left(2 \right)}}$$
Descartamos las soluciones complejas:
$$x_{1} = \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
Las raíces dadas
$$x_{1} = \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
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
$$x_{0} = x_{1} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
=
$$- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
lo sustituimos en la expresión
$$\left(\left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)^{2} - 23 \left(\left(16^{x} - 2 \cdot 4^{x}\right) + 1\right)\right) - 112 > 0$$
$$-112 + \left(- 23 \left(1 + \left(- 2 \cdot 4^{- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}} + 16^{- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}}\right)\right) + \left(1 + \left(- 2 \cdot 4^{- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}} + 16^{- \frac{1}{10} + \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}}\right)\right)^{2}\right) > 0$$
                                                                                                                       2                                                                                                                     
       /                          /             ______________\                          /             ______________\\                             /             ______________\                           /             ______________\    
       |                          |      ___   /        _____ |                          |      ___   /        _____ ||                             |      ___   /        _____ |                           |      ___   /        _____ |    
       |        1    -log(2) + log\2 + \/ 2 *\/  23 + \/ 977  /        1    -log(2) + log\2 + \/ 2 *\/  23 + \/ 977  /|           1    -log(2) + log\2 + \/ 2 *\/  23 + \/ 977  /         1    -log(2) + log\2 + \/ 2 *\/  23 + \/ 977  / > 0
       |      - -- + ------------------------------------------      - -- + ------------------------------------------|         - -- + ------------------------------------------       - -- + ------------------------------------------    
       |        10                    2*log(2)                         10                    2*log(2)                 |           10                    2*log(2)                          10                    2*log(2)                     
-135 + \1 + 16                                                  - 2*4                                                 /  - 23*16                                                  + 46*4                                                     

Entonces
$$x < \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
no se cumple
significa que la solución de la desigualdad será con:
$$x > \frac{- \log{\left(2 \right)} + \log{\left(2 + \sqrt{2} \sqrt{23 + \sqrt{977}} \right)}}{2 \log{\left(2 \right)}}$$
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