Giải thích các bước giải:
$\begin{array}{l}
b)y = 4{\cos ^2}3x - \left( {5{x^2} + 3} \right)\left( {2x - 7} \right)\\
\Rightarrow y' = 4.2\cos 3x.\left( { - 3\sin 3x} \right) - \left( {5.2x.\left( {2x - 7} \right) + \left( {5{x^2} + 3} \right).2} \right)\\
\Rightarrow y' = - 24\sin 3x.\cos 3x - 30{x^2} + 70x - 6\\
c)y = \dfrac{{3x - 2}}{{\sqrt {2x + 5} }} + 3\sin \left( {7x - 3} \right)\\
\Rightarrow y' = \dfrac{{3\sqrt {2x + 5} - \left( {3x - 2} \right).\dfrac{1}{{\sqrt {2x + 5} }}}}{{2x + 5}} + 3.7.\cos \left( {7x - 3} \right)\\
\Rightarrow y' = \dfrac{{3x + 17}}{{\left( {2x + 5} \right)\sqrt {2x + 5} }} + 21\cos \left( {7x - 3} \right)
\end{array}$
