Rút gọn
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n) \( \frac{9x^3 - 18x}{3 \cdot x^4 - 4} \) ;
p) \( \frac{x(x + 3)}{x^2(3 + x)} \) ;
q) \( \frac{x^2 - 2x + 1}{x^2 - 3x + 2} \) .
o) \( P = \frac{x^3 + 8}{x^2 - 2x + 4} - (x - 2) ; \)
u) \( Q = \frac{48(x - 5)^2}{120 - 24x} ; \)
v) \( R = \frac{12x^3y^4(x - y)^2}{18x^2y^5(y - x)} .\)