a) ĐK:\(\begin{cases} x + 2≠0\\ x - 2≠0 \end{cases}\)⇔\(\begin{cases} x ≠ -2\\ x≠ 2 \end{cases}\)

Vậy biểu thức P xác định khi x≠ -2 và x≠ 2

b) P= \(\dfrac{3}{x+2}\)-\(\dfrac{2}{2-x}\)-\(\dfrac{8}{x^2-4}\)

P=\(\dfrac{3}{x+2}\)+\(\dfrac{2}{x-2}\)-\(\dfrac{8}{(x-2)(x+2)}\)

P= \(\dfrac{3(x-2)}{(x-2)(x+2)}\)+\(\dfrac{2(x+2)}{(x-2)(x+2)}\)-\(\dfrac{8}{(x-2)(x+2)}\)

P= \(​​​​\dfrac{3x-6+2x+4-8}{(x-2)(x+2)}\)

P=\(\dfrac{5x-10}{(x-2)(x+2)}\)

P=\(\dfrac{5(x-2)}{(x-2)(x+2)}\)

P=\(\dfrac{5}{x+2}\)

Vậy P=\(\dfrac{5}{x+2}\)