Giải thích các bước giải:
\(\begin{array}{l}
a)\frac{{4x + 1}}{{x - 5}} + \frac{{{x^2} + 2}}{{x - 5}} - \frac{{{x^2} + 3}}{{{x^2} - 25}} = \frac{{4x + 1}}{{x - 5}} + \frac{{{x^2} + 2}}{{x - 5}} - \frac{{{x^2} + 3}}{{(x - 5)(x + 5)}}\\
= \frac{{{x^2} + 4x + 3}}{{x - 5}} - \frac{{{x^2} + 3}}{{(x - 5)(x + 5)}} = \frac{{({x^2} + 4x + 3)(x + 5) - {x^2} - 3}}{{(x - 5)(x + 5)}} = \frac{{{x^3} + 8{x^2} + 23x + 12}}{{{x^2} - 25}}\\
b)\frac{{{x^2} - 6x}}{{x + 6}}.\frac{{2x + 12}}{{x - 6}} = \frac{{x(x - 6)}}{{x + 6}}.\frac{{2(x + 6)}}{{x - 6}} = 2x
\end{array}\)
