$12.2 \lim _{x \rightarrow 4} \frac{\sqrt{x^{2}-7}-3}{x-4}$.

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$12.2 \lim _{x \rightarrow 4} \frac{\sqrt{x^{2}-7}-3}{x-4}$.
12.2 Instruction. Multiply the numerator and denominator of the fraction by $\sqrt{x^{2}-7}+3$

Answer: $\frac{4}{3}$.