Cho hàm số f ( x ) = { x^2 − 1 + 2 m k h i x < 2 √ x + 7 k h i x ≥ 2 ( m là tham số).

7/11

Cho hàm số \(f\left( x \right) = \left\{ \begin{array}{l}{x^2} - 1 + 2m\;{\rm{khi}}\;x < 2\\\sqrt {x + 7} \;\;\;\;\;\;\;{\rm{khi}}\;x \ge 2\end{array} \right.\) (\(m\)là tham số).

a) Khi \(m = - 1\) thì \(\mathop {\lim }\limits_{x \to {2^ - }} f\left( x \right) = 1\).

b) \(\mathop {\lim }\limits_{x \to 3} f\left( x \right) = 5\).

c) Tồn tại \(\mathop {\lim }\limits_{x \to 2} f\left( x \right)\) khi \(m = - 3\).

d) \(\mathop {\lim }\limits_{x \to {2^ + }} f\left( x \right) = 3\).

Nhập câu trả lời ở đây

0/3000 ký tự

Giải thích

a) Khi \(m = - 1\) thì \(\mathop {\lim }\limits_{x \to {2^ - }} f\left( x \right) = \mathop {\lim }\limits_{x \to {2^ - }} \left( {{x^2} - 1 - 2} \right) = \mathop {\lim }\limits_{x \to {2^ - }} \left( {{x^2} - 3} \right) = 1\).

b) \(\mathop {\lim }\limits_{x \to 3} f\left( x \right) = \mathop {\lim }\limits_{x \to 3} \sqrt {x + 7} = \sqrt {10} \).

c) \(\mathop {\lim }\limits_{x \to {2^ + }} f\left( x \right) = \mathop {\lim }\limits_{x \to {2^ + }} \sqrt {x + 7} = 3\); \(\mathop {\lim }\limits_{x \to {2^ - }} f\left( x \right) = \mathop {\lim }\limits_{x \to {2^ - }} \left( {{x^2} - 1 + 2m} \right) = 3 + 2m\); \(f\left( 2 \right) = 3\).

Để tồn tại \(\mathop {\lim }\limits_{x \to 2} f\left( x \right)\) thì \(3 + 2m = 3 \Leftrightarrow m = 0\).

d) \(\mathop {\lim }\limits_{x \to {2^ + }} f\left( x \right) = \mathop {\lim }\limits_{x \to {2^ + }} \sqrt {x + 7} = 3\).

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