Se da la desigualdad:
$$\left(- x^{2} + 5 x\right) \log{\left(\frac{1}{4} \right)} + \left(\sqrt{5}\right)^{\log{\left(3 \right)}} < 0$$
Para resolver esta desigualdad primero hay que resolver la ecuación correspondiente:
$$\left(- x^{2} + 5 x\right) \log{\left(\frac{1}{4} \right)} + \left(\sqrt{5}\right)^{\log{\left(3 \right)}} = 0$$
Resolvemos:
Abramos la expresión en la ecuación
$$\left(- x^{2} + 5 x\right) \log{\left(\frac{1}{4} \right)} + \left(\sqrt{5}\right)^{\log{\left(3 \right)}} = 0$$
Obtenemos la ecuación cuadrática
$$2 x^{2} \log{\left(2 \right)} - 10 x \log{\left(2 \right)} + 5^{\frac{\log{\left(3 \right)}}{2}} = 0$$
Es la ecuación de la forma
a*x^2 + b*x + c = 0
La ecuación cuadrática puede ser resuelta
con la ayuda del discriminante.
Las raíces de la ecuación cuadrática:
$$x_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$x_{2} = \frac{- \sqrt{D} - b}{2 a}$$
donde D = b^2 - 4*a*c es el discriminante.
Como
$$a = 2 \log{\left(2 \right)}$$
$$b = - 10 \log{\left(2 \right)}$$
$$c = 5^{\frac{\log{\left(3 \right)}}{2}}$$
, entonces
D = b^2 - 4 * a * c =
(-10*log(2))^2 - 4 * (2*log(2)) * (5^(log(3)/2)) = 100*log(2)^2 - 8*5^(log(3)/2)*log(2)
Como D > 0 la ecuación tiene dos raíces.
x1 = (-b + sqrt(D)) / (2*a)
x2 = (-b - sqrt(D)) / (2*a)
o
$$x_{1} = \frac{\sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{2} = \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{1} = \frac{\sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{2} = \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{1} = \frac{\sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{2} = \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
Las raíces dadas
$$x_{2} = \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
$$x_{1} = \frac{\sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
son puntos de cambio del signo de desigualdad en las soluciones.
Primero definámonos con el signo hasta el punto extremo izquierdo:
$$x_{0} < x_{2}$$
Consideremos, por ejemplo, el punto
$$x_{0} = x_{2} - \frac{1}{10}$$
=
$$- \frac{1}{10} + \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
=
$$- \frac{1}{10} + \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
lo sustituimos en la expresión
$$\left(- x^{2} + 5 x\right) \log{\left(\frac{1}{4} \right)} + \left(\sqrt{5}\right)^{\log{\left(3 \right)}} < 0$$
$$\left(- \left(- \frac{1}{10} + \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}\right)^{2} + 5 \left(- \frac{1}{10} + \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}\right)\right) \log{\left(\frac{1}{4} \right)} + \left(\sqrt{5}\right)^{\log{\left(3 \right)}} < 0$$
/ 2 \
| / ________________________________ \ / ________________________________ \|
| | / log(3) | | / log(3) ||
log(3) | | / ------ | | / ------ ||
------ | | / 2 2 | | / 2 2 || < 0
2 | 1 | 1 - \/ 100*log (2) - 8*5 *log(2) + 10*log(2)| 5*\- \/ 100*log (2) - 8*5 *log(2) + 10*log(2)/|
5 - |- - - |- -- + ---------------------------------------------------| + -------------------------------------------------------|*log(4)
\ 2 \ 10 4*log(2) / 4*log(2) /
pero
/ 2 \
| / ________________________________ \ / ________________________________ \|
| | / log(3) | | / log(3) ||
log(3) | | / ------ | | / ------ ||
------ | | / 2 2 | | / 2 2 || > 0
2 | 1 | 1 - \/ 100*log (2) - 8*5 *log(2) + 10*log(2)| 5*\- \/ 100*log (2) - 8*5 *log(2) + 10*log(2)/|
5 - |- - - |- -- + ---------------------------------------------------| + -------------------------------------------------------|*log(4)
\ 2 \ 10 4*log(2) / 4*log(2) /
Entonces
$$x < \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
no se cumple
significa que una de las soluciones de nuestra ecuación será con:
$$x > \frac{- \sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}} \wedge x < \frac{\sqrt{- 8 \cdot 5^{\frac{\log{\left(3 \right)}}{2}} \log{\left(2 \right)} + 100 \log{\left(2 \right)}^{2}} + 10 \log{\left(2 \right)}}{4 \log{\left(2 \right)}}$$
_____
/ \
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x2 x1