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Câu hỏi:

16/10/2025 1,051 Lưu

Cho hàm số f ( x ) = ( 3x − 1 )^2 có đạo hàm f ′ ( x ) . a) 2 ∫ − 1 f ′ ( x ) dx = 5 .

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Trả lời:

verified Giải bởi Vietjack

a) \(\int\limits_{ - 1}^2 {f'\left( x \right)dx} = \left. {f\left( x \right)} \right|_{ - 1}^2 = \left. {{{\left( {3x - 1} \right)}^2}} \right|_{ - 1}^2 = 25 - 16 = 9\).

b) \(\int\limits_0^1 {f\left( x \right)dx} = \int\limits_0^1 {{{\left( {3x - 1} \right)}^2}dx} = \left. {\frac{{{{\left( {3x - 1} \right)}^3}}}{9}} \right|_0^1 = \frac{8}{9} - \left( { - \frac{1}{9}} \right) = 1\).

c) Ta có \(\int\limits_0^1 {\left[ {3f\left( x \right) - 1} \right]dx} = 3\int\limits_0^1 {f\left( x \right)dx} - \int\limits_0^1 {1dx} = 3.1 - 1 = 2\).

d) \(\int\limits_{ - 1}^2 {\left[ {f'\left( x \right) - 2xf\left( x \right)} \right]dx} = \int\limits_{ - 1}^2 {f'\left( x \right)dx} - \int\limits_{ - 1}^2 {2x{{\left( {3x - 1} \right)}^2}dx} = 9 - \frac{{69}}{2} = - \frac{{51}}{2}\).

Đáp án: a) Sai;   b) Sai;    c) Sai;    d) Đúng.