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Câu hỏi: Cho $\int{f\left( x \right)}dx=\dfrac{{{x}^{5}}}{5}+{{e}^{x}}-cosx+C$ thì $f\left( x \right)$ bằng
A. $\dfrac{{{x}^{6}}}{30}+{{e}^{x}}+\sin x$.
B. ${{x}^{4}}+{{e}^{x}}+\sin x$.
C. ${{x}^{4}}+{{e}^{x}}-\sin x$.
D. $\dfrac{{{x}^{6}}}{30}+{{e}^{x}}-\sin x$.
A. $\dfrac{{{x}^{6}}}{30}+{{e}^{x}}+\sin x$.
B. ${{x}^{4}}+{{e}^{x}}+\sin x$.
C. ${{x}^{4}}+{{e}^{x}}-\sin x$.
D. $\dfrac{{{x}^{6}}}{30}+{{e}^{x}}-\sin x$.
Ta có: $f\left( x \right)={{\left( \dfrac{{{x}^{5}}}{5}+{{e}^{x}}-cosx+C \right)}^{\prime }}={{x}^{4}}+{{e}^{x}}+\sin x.$
Đáp án B.