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Câu hỏi: Cho hàm số $f\left( x \right)=3\cos x-{{3}^{x}}$. Khẳng định nào dưới đây đúng?
A. $\int{f\left( x \right)\text{d}x}=-3\sin x+\dfrac{{{3}^{x}}}{\ln 3}+C$.
B. $\int{f\left( x \right)\text{d}x}=3\sin x+\dfrac{{{3}^{x}}}{\ln 3}+C$.
C. $\int{f\left( x \right)\text{d}x}=-3\sin x-\dfrac{{{3}^{x}}}{\ln 3}+C$.
D. $\int{f\left( x \right)\text{d}x}=3\sin x-\dfrac{{{3}^{x}}}{\ln 3}+C$.
A. $\int{f\left( x \right)\text{d}x}=-3\sin x+\dfrac{{{3}^{x}}}{\ln 3}+C$.
B. $\int{f\left( x \right)\text{d}x}=3\sin x+\dfrac{{{3}^{x}}}{\ln 3}+C$.
C. $\int{f\left( x \right)\text{d}x}=-3\sin x-\dfrac{{{3}^{x}}}{\ln 3}+C$.
D. $\int{f\left( x \right)\text{d}x}=3\sin x-\dfrac{{{3}^{x}}}{\ln 3}+C$.
Ta có $\int{f\left( x \right)\text{d}x}=\int{(3\cos x-{{3}^{x}})dx=}3\sin x-\dfrac{{{3}^{x}}}{\ln 3}+C$.
Đáp án D.