\[\boxed{\mathbf{15}\mathbf{.}}\]
\[\textbf{а)}\ \frac{2\sqrt{0,5 - x}}{(x - 4)(x + 1)} =\]
\[= \frac{\sqrt{0,5 - x}}{(x - 2)(x + 2)}\]
\[1)\ x \neq 4;x \neq - 1;\]
\[x \neq 2;\ \ x \neq - 2.\]
\[0,5 - x \geq 0\]
\[x \leq 0,5.\]
\[\sqrt{0,5 - x}\left( x^{2} + 3x - 4 \right) = 0\]
\[\sqrt{0,5 - x} = 0\]
\[0,5 - x = 0\]
\[x = 0,5.\]
\[x^{2} + 3x - 4 = 0\]
\[x_{1} + x_{2} = - 3;\ \ x_{1} \cdot x_{2} = - 4\]
\[x_{1} = - 4;\ \ \]
\[x_{2} = 1\ (не\ подходит).\]
\[Ответ:x = - 4;x = 0,5.\]
\[\textbf{б)}\ \frac{4\sqrt{x - 10}}{(x - 4)(x + 3)} =\]
\[= \frac{3\sqrt{x - 10}}{(x - 3)(x - 2)}\]
\[1)\ x \neq 4;x \neq - 3;\]
\[x \neq 3;x \neq 2.\]
\[x - 10 \geq 0\]
\[x \geq 10.\]
\[\sqrt{x - 10}\left( x^{2} - 17x + 60 \right) = 0\]
\[\sqrt{x - 10} = 0\]
\[x - 10 = 0\]
\[x = 10.\]
\[x^{2} - 17x + 60 = 0\]
\[x_{1} + x_{2} = 17;\ \ x_{1} \cdot x_{2} = 60\]
\[x_{1} = 5\ (не\ подходит);\]
\[x_{2} = 12.\]
\[Ответ:x = 10;x = 12.\]