Cho hàm số f ( x ) = ( 4 x + 1 )^ 3 ( 2 x + 1 ) ^4 ( 3 + 2 x ) ^7 . Tính lim x → − ∞ f ( x ) .

12/22

Cho hàm số \(f\left( x \right) = \frac{{{{\left( {4x + 1} \right)}^3}{{\left( {2x + 1} \right)}^4}}}{{{{\left( {3 + 2x} \right)}^7}}}\). Tính \(\mathop {\lim }\limits_{x \to - \infty } f\left( x \right)\).

\(2\).

\(8\).

\(4\).

\(0\).

Giải thích

Chọn B

\(\mathop {\lim }\limits_{x \to - \infty } f\left( x \right) = \mathop {\lim }\limits_{x \to - \infty } \frac{{{{\left( {4x + 1} \right)}^3}{{\left( {2x + 1} \right)}^4}}}{{{{\left( {3 + 2x} \right)}^7}}} = \mathop {\lim }\limits_{x \to - \infty } \frac{{{{\left( {4 + \frac{1}{x}} \right)}^3}{{\left( {2 + \frac{1}{x}} \right)}^4}}}{{{{\left( {\frac{3}{x} + 2} \right)}^7}}} = {2^3} = 8\).