Câu hỏi 33.3

\(y = \left( {x - 2} \right)\sqrt {{x^2} + x + 3} \)

\(\begin{array}{l}y' = \sqrt {{x^2} + x + 3}  + \left( {x - 2} \right).\frac{{2x + 1}}{{2\sqrt {{x^2} + x + 3} }}\\\,\,\,\,\, = \frac{{2\left( {{x^2} + x + 3} \right) + \left( {x - 2} \right)\left( {2x + 1} \right)}}{{2\sqrt {{x^2} + x + 3} }}\\\,\,\,\,\, = \frac{{2{x^2} + 2x + 6 + 2{x^2} + x - 4x - 2}}{{2\sqrt {{x^2} + x + 3} }}\\\,\,\,\,\, = \frac{{4{x^2} - x + 4}}{{2\sqrt {{x^2} + x + 3} }}\end{array}\)

Chọn A.