Solución detallada
Para cada expresión dentro del módulo en la ecuación
admitimos los casos cuando la expresión correspondiente es ">= 0" o "< 0",
resolvemos las ecuaciones obtenidas.
1.
$$x \geq 0$$
o
$$0 \leq x \wedge x < \infty$$
obtenemos la ecuación
$$- a + 7 x + \sqrt{1 - 2 x} = 0$$
simplificamos, obtenemos
$$- a + 7 x + \sqrt{1 - 2 x} = 0$$
la resolución en este intervalo:
$$x_{1} = \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{2} = \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
2.
$$x < 0$$
o
$$-\infty < x \wedge x < 0$$
obtenemos la ecuación
$$- a + 7 \left(- x\right) + \sqrt{1 - 2 x} = 0$$
simplificamos, obtenemos
$$- a - 7 x + \sqrt{1 - 2 x} = 0$$
la resolución en este intervalo:
$$x_{3} = - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
$$x_{4} = - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
Entonces la respuesta definitiva es:
$$x_{1} = \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{2} = \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49}$$
$$x_{3} = - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
$$x_{4} = - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49}$$
// ___________ ___ __________ \ // ___________ ___ __________ \
|| 1 a \/ 50 + 14*a 1 a \/ 2 *\/ 25 + 7*a | || 1 a \/ 50 + 14*a 1 a \/ 2 *\/ 25 + 7*a |
||- -- - - - ------------- for -- + - + ------------------ > 0| ||- -- - - - ------------- for -- + - + ------------------ > 0|
x1 = I*im|< 49 7 49 49 7 49 | + re|< 49 7 49 49 7 49 |
|| | || |
|| nan otherwise | || nan otherwise |
\\ / \\ /
$$x_{1} = \operatorname{re}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} - \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
// ___________ ___ __________ \ // ___________ ___ __________ \
|| 1 a \/ 50 + 14*a 1 a \/ 2 *\/ 25 + 7*a | || 1 a \/ 50 + 14*a 1 a \/ 2 *\/ 25 + 7*a |
||- -- - - + ------------- for -- + - - ------------------ > 0| ||- -- - - + ------------- for -- + - - ------------------ > 0|
x2 = I*im|< 49 7 49 49 7 49 | + re|< 49 7 49 49 7 49 |
|| | || |
|| nan otherwise | || nan otherwise |
\\ / \\ /
$$x_{2} = \operatorname{re}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} - \frac{a}{7} + \frac{\sqrt{14 a + 50}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} - \frac{\sqrt{2} \sqrt{7 a + 25}}{49} + \frac{1}{49} > 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
// ___________ ___ __________ \ // ___________ ___ __________ \
|| 1 \/ 50 - 14*a a 1 a \/ 2 *\/ 25 - 7*a | || 1 \/ 50 - 14*a a 1 a \/ 2 *\/ 25 - 7*a |
||- -- - ------------- + - for -- - - + ------------------ <= 0| ||- -- - ------------- + - for -- - - + ------------------ <= 0|
x3 = I*im|< 49 49 7 49 7 49 | + re|< 49 49 7 49 7 49 |
|| | || |
|| nan otherwise | || nan otherwise |
\\ / \\ /
$$x_{3} = \operatorname{re}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} - \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: - \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} + \frac{1}{49} \leq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
// ___________ ___ __________ \ // ___________ ___ __________ \
|| 1 a \/ 50 - 14*a 1 a \/ 2 *\/ 25 - 7*a | || 1 a \/ 50 - 14*a 1 a \/ 2 *\/ 25 - 7*a |
||- -- + - + ------------- for - -- + - + ------------------ >= 0| ||- -- + - + ------------- for - -- + - + ------------------ >= 0|
x4 = I*im|< 49 7 49 49 7 49 | + re|< 49 7 49 49 7 49 |
|| | || |
|| nan otherwise | || nan otherwise |
\\ / \\ /
$$x_{4} = \operatorname{re}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)} + i \operatorname{im}{\left(\begin{cases} \frac{a}{7} + \frac{\sqrt{50 - 14 a}}{49} - \frac{1}{49} & \text{for}\: \frac{a}{7} + \frac{\sqrt{2} \sqrt{25 - 7 a}}{49} - \frac{1}{49} \geq 0 \\\text{NaN} & \text{otherwise} \end{cases}\right)}$$
x4 = re(Piecewise((a/7 + sqrt(50 - 14*a/49 - 1/49, a/7 + sqrt(2)*sqrt(25 - 7*a)/49 - 1/49 >= 0), (nan, True))) + i*im(Piecewise((a/7 + sqrt(50 - 14*a)/49 - 1/49, a/7 + sqrt(2)*sqrt(25 - 7*a)/49 - 1/49 >= 0), (nan, True))))