$\text{ĐKXĐ: $x \neq -1; x \neq 2$ }$
$\text{Từ pt (1) }$ $⇔ \frac{2 -x}{(x +1).(2 -x)} + \frac{5.(x +1)}{(x +1).(2 -x)} = \frac{15}{(x +1).(2 -x)}$
$⇒ 2 -x +5.(x +1) = 15$
$⇔ 2 -x +5x +5 = 15$
$⇔ 4x = 8$
$⇔ x = 2$ $\text{(Ko t/m đkxđ) }$
$\text{Vậy S = ∅ }$