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Câu hỏi: Tìm họ nguyên hàm $\int{x\left( 3x+1 \right) \text{d}x}$.
A. $\dfrac{3}{4}{{x}^{4}}+\dfrac{1}{2}{{x}^{3}}+C$
B. ${{x}^{3}}+\dfrac{1}{2}{{x}^{2}}+C$
C. ${{x}^{3}}+{{x}^{2}}+C$
D. $3{{x}^{4}}+\dfrac{1}{2}{{x}^{3}}+C$
A. $\dfrac{3}{4}{{x}^{4}}+\dfrac{1}{2}{{x}^{3}}+C$
B. ${{x}^{3}}+\dfrac{1}{2}{{x}^{2}}+C$
C. ${{x}^{3}}+{{x}^{2}}+C$
D. $3{{x}^{4}}+\dfrac{1}{2}{{x}^{3}}+C$
$\int{x\left( 3x+1 \right) \text{d}x}$ $=\int{\left( 3{{x}^{2}}+x \right) \text{d}x}$ $={{x}^{3}}+\dfrac{1}{2}{{x}^{2}}+C$.
Đáp án B.