Ta có
P = ( 4 x + 1 ) 3 – ( 4 x + 3 ) ( 16 x 2 + 3 ) = ( 4 x ) 3 + 3 . ( 4 x ) 2 . 1 + 3 . 4 x . 1 2 + 1 3 – ( 64 x 3 + 12 x + 48 x 2 + 9 ) = 64 x 3 + 48 x 2 + 12 x + 1 – 64 x 3 – 12 x – 48 x 2 – 9 = - 8
Nên P = -8
Q = ( x – 2 ) 3 – x ( x + 1 ) ( x – 1 ) + 6 x ( x – 3 ) + 5 x = x 3 – 3 . x 2 . 2 + 3 x . 2 2 – 2 3 – x ( x 2 – 1 ) + 6 x 2 – 18 x + 5 x = x 3 – 6 x 2 + 12 x – 8 – x 3 + x + 6 x 2 – 18 x + 5 x = - 8
=> Q = -8
Vậy P = Q
Đáp án cần chọn là: A