Đáp án:

\(\begin{array}{l}
a)x \ne \left\{ { - 5;0} \right\}\\
b)\dfrac{{{x^3} + 4{x^2} - 50}}{{2x\left( {x + 5} \right)}}\\
c)2,726421318
\end{array}\)

Giải thích các bước giải:

\(\begin{array}{l}
a)DK:x \ne \left\{ { - 5;0} \right\}\\
b)P = \dfrac{{{x^2} + 2x}}{{2x + 10}} + \dfrac{{x - 5}}{x}\\
 = \dfrac{{{x^3} + 2{x^2} + 2\left( {x - 5} \right)\left( {x + 5} \right)}}{{2x\left( {x + 5} \right)}}\\
 = \dfrac{{{x^3} + 2{x^2} + 2\left( {{x^2} - 25} \right)}}{{2x\left( {x + 5} \right)}}\\
 = \dfrac{{{x^3} + 2{x^2} + 2{x^2} - 50}}{{2x\left( {x + 5} \right)}}\\
 = \dfrac{{{x^3} + 4{x^2} - 50}}{{2x\left( {x + 5} \right)}}\\
c)P = 0\\
 \to \dfrac{{{x^3} + 4{x^2} - 50}}{{2x\left( {x + 5} \right)}} = 0\\
 \to {x^3} + 4{x^2} - 50 = 0\\
 \to 2,726421318
\end{array}\)