` a) ` ` P(x) = 0 `
` => 4x - 1/2 = 0 `
` => 4x = 1/2 `
` => x = 1/8 `
` b) ` ` Q(x) = 0 `
` => (x - 1)(x + 1) = 0 `
` => ` \(\left[ \begin{array}{l}x=1\\x=-1\end{array} \right.\)
` c) ` ` A(x) = 0 `
` => -12x + 18 = 0 `
` => x = 3/2 `
` d) ` ` B(x) = 0 `
` => -(x^{2}) + 16 = 0 `
` => -(x^{2}) = -16 `
` => x^{2} = 16 `
` => x = ` \(\left[ \begin{array}{l}x=4\\x=-4\end{array} \right.\)
` e) ` ` C(x) = 0 `
` => 3x^{2} + 12 = 0 `
` => x^{2} = -4 ` (vô lý)
` => ` Vô nghiệm