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4^x+2^(x+1)+4a-a^2=0 la ecuación

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Solución numérica:

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Solución

Ha introducido [src]
 x    x + 1          2    
4  + 2      + 4*a - a  = 0
$$- a^{2} + \left(4 a + \left(2^{x + 1} + 4^{x}\right)\right) = 0$$
Solución detallada
Tenemos la ecuación:
$$- a^{2} + \left(4 a + \left(2^{x + 1} + 4^{x}\right)\right) = 0$$
o
$$- a^{2} + \left(4 a + \left(2^{x + 1} + 4^{x}\right)\right) = 0$$
Sustituimos
$$v = 2^{x}$$
obtendremos
$$- a^{2} + 4 a + v^{2} + 2 v = 0$$
o
$$- a^{2} + 4 a + v^{2} + 2 v = 0$$
Es la ecuación de la forma
a*v^2 + b*v + c = 0

La ecuación cuadrática puede ser resuelta
con la ayuda del discriminante.
Las raíces de la ecuación cuadrática:
$$v_{1} = \frac{\sqrt{D} - b}{2 a}$$
$$v_{2} = \frac{- \sqrt{D} - b}{2 a}$$
donde D = b^2 - 4*a*c es el discriminante.
Como
$$a = 1$$
$$b = 2$$
$$c = - a^{2} + 4 a$$
, entonces
D = b^2 - 4 * a * c = 

(2)^2 - 4 * (1) * (-a^2 + 4*a) = 4 - 16*a + 4*a^2

La ecuación tiene dos raíces.
v1 = (-b + sqrt(D)) / (2*a)

v2 = (-b - sqrt(D)) / (2*a)

o
$$v_{1} = \frac{\sqrt{4 a^{2} - 16 a + 4}}{2} - 1$$
$$v_{2} = - \frac{\sqrt{4 a^{2} - 16 a + 4}}{2} - 1$$
hacemos cambio inverso
$$2^{x} = v$$
o
$$x = \frac{\log{\left(v \right)}}{\log{\left(2 \right)}}$$
Entonces la respuesta definitiva es
$$x_{1} = \frac{\log{\left(\frac{\sqrt{4 a^{2} - 16 a + 4}}{2} - 1 \right)}}{\log{\left(2 \right)}} = \frac{\log{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}$$
$$x_{2} = \frac{\log{\left(- \frac{\sqrt{4 a^{2} - 16 a + 4}}{2} - 1 \right)}}{\log{\left(2 \right)}} = \frac{\log{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}$$
Gráfica
Suma y producto de raíces [src]
suma
   /|       ______________|\        /        ______________\      /|        ______________|\        /        ______________\
   ||      /      2       ||        |       /      2       |      ||       /      2       ||        |       /      2       |
log\|1 + \/  1 + a  - 4*a |/   I*arg\-1 - \/  1 + a  - 4*a /   log\|-1 + \/  1 + a  - 4*a |/   I*arg\-1 + \/  1 + a  - 4*a /
---------------------------- + ----------------------------- + ----------------------------- + -----------------------------
           log(2)                          log(2)                          log(2)                          log(2)           
$$\left(\frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} - 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}\right) + \left(\frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} + 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}\right)$$
=
   /|       ______________|\      /|        ______________|\        /        ______________\        /        ______________\
   ||      /      2       ||      ||       /      2       ||        |       /      2       |        |       /      2       |
log\|1 + \/  1 + a  - 4*a |/   log\|-1 + \/  1 + a  - 4*a |/   I*arg\-1 + \/  1 + a  - 4*a /   I*arg\-1 - \/  1 + a  - 4*a /
---------------------------- + ----------------------------- + ----------------------------- + -----------------------------
           log(2)                          log(2)                          log(2)                          log(2)           
$$\frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} - 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} + 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}$$
producto
/   /|       ______________|\        /        ______________\\ /   /|        ______________|\        /        ______________\\
|   ||      /      2       ||        |       /      2       || |   ||       /      2       ||        |       /      2       ||
|log\|1 + \/  1 + a  - 4*a |/   I*arg\-1 - \/  1 + a  - 4*a /| |log\|-1 + \/  1 + a  - 4*a |/   I*arg\-1 + \/  1 + a  - 4*a /|
|---------------------------- + -----------------------------|*|----------------------------- + -----------------------------|
\           log(2)                          log(2)           / \            log(2)                          log(2)           /
$$\left(\frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} - 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}\right) \left(\frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} + 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}\right)$$
=
/     /        ______________\      /|        ______________|\\ /     /        ______________\      /|       ______________|\\
|     |       /      2       |      ||       /      2       ||| |     |       /      2       |      ||      /      2       |||
\I*arg\-1 + \/  1 + a  - 4*a / + log\|-1 + \/  1 + a  - 4*a |//*\I*arg\-1 - \/  1 + a  - 4*a / + log\|1 + \/  1 + a  - 4*a |//
------------------------------------------------------------------------------------------------------------------------------
                                                              2                                                               
                                                           log (2)                                                            
$$\frac{\left(\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} - 1}\right| \right)} + i \arg{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}\right) \left(\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} + 1}\right| \right)} + i \arg{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}\right)}{\log{\left(2 \right)}^{2}}$$
(i*arg(-1 + sqrt(1 + a^2 - 4*a)) + log(Abs(-1 + sqrt(1 + a^2 - 4*a))))*(i*arg(-1 - sqrt(1 + a^2 - 4*a)) + log(Abs(1 + sqrt(1 + a^2 - 4*a))))/log(2)^2
Respuesta rápida [src]
        /|       ______________|\        /        ______________\
        ||      /      2       ||        |       /      2       |
     log\|1 + \/  1 + a  - 4*a |/   I*arg\-1 - \/  1 + a  - 4*a /
x1 = ---------------------------- + -----------------------------
                log(2)                          log(2)           
$$x_{1} = \frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} + 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(- \sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}$$
        /|        ______________|\        /        ______________\
        ||       /      2       ||        |       /      2       |
     log\|-1 + \/  1 + a  - 4*a |/   I*arg\-1 + \/  1 + a  - 4*a /
x2 = ----------------------------- + -----------------------------
                 log(2)                          log(2)           
$$x_{2} = \frac{\log{\left(\left|{\sqrt{a^{2} - 4 a + 1} - 1}\right| \right)}}{\log{\left(2 \right)}} + \frac{i \arg{\left(\sqrt{a^{2} - 4 a + 1} - 1 \right)}}{\log{\left(2 \right)}}$$
x2 = log(Abs(sqrt(a^2 - 4*a + 1) - 1))/log(2) + i*arg(sqrt(a^2 - 4*a + 1) - 1)/log(2)