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Câu hỏi: Tìm nguyên hàm của hàm số $f\left( x \right)={{\text{e}}^{x}}\left( 1+{{\text{e}}^{-x}} \right)$.
A. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{-x}}+C$.
B. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+x+C$.
C. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+{{\text{e}}^{-x}}+C$.
D. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+C$.
A. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{-x}}+C$.
B. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+x+C$.
C. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+{{\text{e}}^{-x}}+C$.
D. $\int{f\left( x \right)\text{d}x}={{\text{e}}^{x}}+C$.
Ta có $\int{f\left( x \right)\text{d}x}=\int{\left( {{\text{e}}^{x}}+1 \right)\text{d}x}={{\text{e}}^{x}}+x+C$.
Đáp án B.