a: \(A = \left(\right. a + 3 \left.\right) \left(\right. 9 a - 8 \left.\right) - \left(\right. a + 2 \left.\right) \left(\right. 9 a - 1 \left.\right)\)

\(= 9 a^{2} - 8 a + 27 a - 24 - \left(\right. 9 a^{2} - a + 18 a - 2 \left.\right)\)

\(= 9 a^{2} + 19 a - 24 - 9 a^{2} - 17 a + 2 = 2 a - 22\)

Thay a=-3 vào A, ta được:

\(A = 2 \cdot \left(\right. - 3 \left.\right) - 22 = - 6 - 22 = - 28\)

b: \(Q = \left(\right. 3 x - 5 \left.\right) \left(\right. 2 x + 11 \left.\right) - \left(\right. 2 x + 3 \left.\right) \left(\right. 3 x + 7 \left.\right)\)

\(= 6 x^{2} + 33 x - 10 x - 55 - \left(\right. 6 x^{2} + 14 x + 9 x + 21 \left.\right)\)

\(= 6 x^{2} + 23 x - 55 - 6 x^{2} - 23 x - 21\)

=-55-21

=-76

=>Q không phụ thuộc vào biến x