2) \( \lim _{x \rightarrow+\infty} \frac{x^{3}+3}{\sqrt{x+4}} \) 3) \( \lim _{x \rightarrow-\infty} \frac{1-2 x}{x^{3}+2} \) 4) \( \lim _{x \rightarrow-3} \frac{\sqrt{x+3}}{x^{2}-9} \)
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The Deep Dive
For the first limit, as \( x \) approaches infinity, the term \( x^3 \) in the numerator dominates, and the limit can be simplified to \( \lim _{x \rightarrow+\infty} \frac{x^{3}}{\sqrt{x}} = \lim _{x \rightarrow+\infty} \frac{x^{3}}{x^{1/2}} = \lim _{x \rightarrow+\infty} x^{2.5} \), which tends towards infinity. Thus, the result is \( +\infty \). In the second limit, as \( x \) approaches negative infinity, the term \(-2x\) in the numerator grows more significant than the \( 1 \), while in the denominator, the \( x^3 \) term dominates as well. This leads to \( \lim _{x \rightarrow-\infty} \frac{-2x}{x^3} = \lim _{x \rightarrow-\infty} \frac{-2}{x^2} \), which results in \( 0 \). For the last limit, as \( x \) approaches -3, the expression becomes \( \frac{\sqrt{x+3}}{(x-3)(x+3)} \). Thus, the numerator approaches \( 0 \) and the denominator approaches \( 0 \), leading us to use L'Hôpital's Rule or evaluate the limit more closely, which gives us an undefined form that simplifies to \( \frac{1}{-6} \) through further calculations. Hence, the limit is \(-\frac{1}{6}\).