Chứng minh A,B ∉ x

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1) \( m, A, B \in \mathbb{R} \)

a) \( A = (3+2x)(x-5) + 2x(3-x) + x + 14 \)

b) \( B = 3(1-2x)(4-3x) + (3-2x)(3x-1) - 7(2x-1) \)