Cách làm cho bạn:
$\frac{2x + 6}{x^{2} - 4}$ = $\frac{2x + 6}{(x – 2)(x + 2)}$ = $\frac{4x + 12}{2(x – 2)(x + 2)}$ = $\frac{5x + 10 – x + 2}{2(x – 2)(x + 2)}$ = $\frac{5(x + 2) – (x – 2)}{2(x – 2)(x + 2)}$ = $\frac{5}{2(x – 2)}$ - $\frac{1}{2(x + 2)}$.
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