Giải thích các bước giải:
\(\begin{array}{l}
a,\\
\mathop {\lim }\limits_{x \to 1} \frac{{{x^2} + 7x - 8}}{{x - 1}}\\
= \mathop {\lim }\limits_{x \to 1} \frac{{\left( {x - 1} \right)\left( {x + 8} \right)}}{{x - 1}}\\
= \mathop {\lim }\limits_{x \to 1} \left( {x + 8} \right)\\
= 1 + 8 = 9\\
b,\\
\mathop {\lim }\limits_{x \to 4} \frac{{\sqrt {2x + 1} - 3}}{{x - 4}}\\
= \mathop {\lim }\limits_{x \to 4} \frac{{\frac{{2x + 1 - {3^2}}}{{\sqrt {2x + 1} + 3}}}}{{x - 4}}\\
= \mathop {\lim }\limits_{x \to 4} \frac{{\frac{{2\left( {x - 4} \right)}}{{\sqrt {2x + 1} + 3}}}}{{x - 4}}\\
= \mathop {\lim }\limits_{x \to 4} \frac{2}{{\sqrt {2x + 1} + 3}}\\
= \frac{2}{{\sqrt {2.4 + 1} + 3}}\\
= \frac{2}{6} = \frac{1}{3}
\end{array}\)
