下列说法正确的是 \((\qquad)\)
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【出处】
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【答案】
ACD
【解析】
对于A:$ y' = \left(2{x^2} - 5x + 1 + 4x - 5\right){{\mathrm{e}}^x} = \left(2{x^2} - x - 4\right){{\mathrm{e}}^x} $;
对于B:因为\[f\left(x\right) = {x^{ - \frac{3}{2}}} - x + \ln x,\]所以\[f'\left(x\right) = - \dfrac{3}{2}{x^{ - \frac{5}{2}}} - 1 + \dfrac{1}{x}.\]对于C:根据函数求导法则,有\[\begin{split} y' &= {\left[ {{{\sin }^2}\left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)} \right]^\prime } = 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot {\left[ {\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)} \right]^\prime } \\ &= 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot \cos \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot {\left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)^\prime }\\ &= 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot \cos \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot 2\\ &=2\sin \left( {4x + \dfrac{{2{\mathrm{\pi }}}}{3}} \right).\end{split} \]对于D:对原函数分离常数,得$$y = - 1 + \dfrac{2}{{\ln x + 1}},$$根据除法求导法则,得$$y' = - \dfrac{{2\left(\ln x + 1\right)'}}{{{{\left(\ln x + 1\right)}^2}}} = \dfrac{{ - 2}}{{x{{\left(\ln x + 1\right)}^2}}}.$$
对于B:因为\[f\left(x\right) = {x^{ - \frac{3}{2}}} - x + \ln x,\]所以\[f'\left(x\right) = - \dfrac{3}{2}{x^{ - \frac{5}{2}}} - 1 + \dfrac{1}{x}.\]对于C:根据函数求导法则,有\[\begin{split} y' &= {\left[ {{{\sin }^2}\left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)} \right]^\prime } = 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot {\left[ {\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)} \right]^\prime } \\ &= 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot \cos \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot {\left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right)^\prime }\\ &= 2\sin \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot \cos \left( {2x + \dfrac{{\mathrm{\pi }}}{3}} \right) \cdot 2\\ &=2\sin \left( {4x + \dfrac{{2{\mathrm{\pi }}}}{3}} \right).\end{split} \]对于D:对原函数分离常数,得$$y = - 1 + \dfrac{2}{{\ln x + 1}},$$根据除法求导法则,得$$y' = - \dfrac{{2\left(\ln x + 1\right)'}}{{{{\left(\ln x + 1\right)}^2}}} = \dfrac{{ - 2}}{{x{{\left(\ln x + 1\right)}^2}}}.$$
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