Đáp án:
\(\begin{array}{l}
b)\quad \lim\limits_{x\to -2}\dfrac{x+2}{x^2 +5x +6} = 1\\
e)\quad \lim\limits_{x\to 2}\dfrac{x^4-16}{8-x^3} = -\dfrac83
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
b)\quad \lim\limits_{x\to -2}\dfrac{x+2}{x^2 +5x +6}\\
= \lim\limits_{x\to -2}\dfrac{x+2}{(x+3)(x+2)}\\
= \lim\limits_{x\to -2}\dfrac{1}{x+3}\\
= \dfrac{1}{-2 +3} = 1\\
e)\quad \lim\limits_{x\to 2}\dfrac{x^4-16}{8-x^3}\\
=\lim\limits_{x\to 2}\dfrac{(x-2)(x+2)(x^2+4)}{-(x-2)(x^2 +2x + 4)}\\
= \lim\limits_{x\to 2}\dfrac{(x+2)(x^2+4)}{-(x^2 +2x + 4)}\\
=\dfrac{(2+2)(2^2 + 4)}{-(2^2 + 2.2 + 4)} = -\dfrac83
\end{array}\)
