Đáp án:
$\begin{array}{l}
3)\dfrac{{x + 10}}{{x - 2}} + \dfrac{{x - 18}}{{x - 2}} + \dfrac{{x + 2}}{{{x^2} - 4}}\\
= \dfrac{{x + 10 + x - 18}}{{x - 2}} + \dfrac{{x + 2}}{{\left( {x - 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{{2x - 8}}{{x - 2}} + \dfrac{1}{{x - 2}}\\
= \dfrac{{2x - 7}}{{x - 2}}\\
4)\dfrac{{3 - 3x}}{{2x}} + \dfrac{{3x - 1}}{{2x - 1}} + \dfrac{{11x - 5}}{{2x - 4{x^2}}}\\
= \dfrac{{\left( {3 - 3x} \right).\left( {2x - 1} \right) + \left( {3x - 1} \right).2x - 11x + 5}}{{2x\left( {2x - 1} \right)}}\\
= \dfrac{{6x - 3 - 6{x^2} + 3x + 6{x^2} - 2x - 11x + 5}}{{2x\left( {2x - 1} \right)}}\\
= \dfrac{{ - 4x + 2}}{{2x\left( {2x - 1} \right)}}\\
= \dfrac{{ - 2\left( {2x - 1} \right)}}{{2x\left( {2x - 1} \right)}}\\
= \dfrac{{ - 1}}{x}\\
5)\dfrac{2}{{x + 2}} + \dfrac{4}{{x - 2}} + \dfrac{{5x + 2}}{{4 - {x^2}}}\\
= \dfrac{{2\left( {x - 2} \right) + 4\left( {x + 2} \right) - 5x - 2}}{{\left( {x - 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{{x + 2}}{{\left( {x - 2} \right)\left( {x + 2} \right)}}\\
= \dfrac{1}{{x - 2}}
\end{array}$
