Giải thích các bước giải:
a,
ĐKXĐ:
\(\left\{ \begin{array}{l}
x + 3 \ne 0\\
{x^2} + x - 6 \ne 0\\
2 - x \ne 0
\end{array} \right. \Leftrightarrow \left\{ \begin{array}{l}
x \ne - 3\\
x \ne 2
\end{array} \right.\)
b,
Ta có:
\(\begin{array}{l}
A = \frac{{x + 2}}{{x + 3}} - \frac{5}{{{x^2} + x - 6}} - \frac{1}{{2 - x}}\\
= \frac{{x + 2}}{{x + 3}} - \frac{5}{{\left( {x + 3} \right)\left( {x - 2} \right)}} + \frac{1}{{x - 2}}\\
= \frac{{\left( {x + 2} \right)\left( {x - 2} \right) - 5 + \left( {x + 3} \right)}}{{\left( {x + 3} \right)\left( {x - 2} \right)}}\\
= \frac{{{x^2} - 4 - 5 + x + 3}}{{\left( {x + 3} \right)\left( {x - 2} \right)}}\\
= \frac{{{x^2} + x - 6}}{{{x^2} + x - 6}} = 1
\end{array}\)
