Cho hàm số\(\;f\left( x \right) = \frac{{3{x^2} + 2x + 1}}{{2\sqrt {3{x^3} + 2{x^2} + 1} }}\). Giá trị\[\;f'\left( 0 \right)\]là:

Hướng dẫn giải:

Chọn B

\[\;f'\left( 0 \right) = \frac{{{{\left( {3{x^2} + 2x + 1} \right)}^\prime }.2\sqrt {3{x^3} + 2{x^2} + 1} - \left( {3{x^2} + 2x + 1} \right).{{\left( {2\sqrt {3{x^3} + 2{x^2} + 1} } \right)}^\prime }}}{{{{\left( {2\sqrt {3{x^3} + 2{x^2} + 1} } \right)}^2}}}\]

\( = \frac{{\left( {6x + 2} \right)2\sqrt {3{x^3} + 2{x^2} + 1} - \left( {3{x^2} + 2x + 1} \right)\frac{{9{x^2} + 4x}}{{\sqrt {3{x^3} + 2{x^2} + 1} }}}}{{{{\left( {2\sqrt {3{x^3} + 2{x^2} + 1} } \right)}^2}}} = \frac{{9{x^4} + 6{x^3} - 9{x^2} + 8x + 4}}{{4\left( {3{x^3} + 2{x^2} + 1} \right)\sqrt {3{x^3} + 2{x^2} + 1} }}\).

\[\;f'\left( 0 \right) = \frac{4}{8} = \frac{1}{2}.\]