Questions: Find the limit, if it exists. (If an answer does not exist, enter DNE.)
lim as x approaches -∞ of (3x) / sqrt(x^2 - x)
Transcript text: Find the limit, if it exists. (If an answer does not exist, enter DNE.)
\[
\lim _{x \rightarrow-\infty} \frac{3 x}{\sqrt{x^{2}-x}}
\]
$\square$
Solution
Solution Steps
To find the limit of the given expression as \( x \) approaches \(-\infty\), we can simplify the expression by dividing the numerator and the denominator by \( x \). This will help us analyze the behavior of the function as \( x \) becomes very large in the negative direction. After simplification, we can evaluate the limit of the resulting expression.
Step 1: Simplifying the Expression
We start with the limit:
\[
\lim_{x \rightarrow -\infty} \frac{3x}{\sqrt{x^2 - x}}
\]
To simplify, we divide the numerator and the denominator by \( x \):
\[
\frac{3x}{\sqrt{x^2 - x}} = \frac{3}{\sqrt{1 - \frac{1}{x}}}
\]
Step 2: Evaluating the Limit
As \( x \) approaches \(-\infty\), the term \(\frac{1}{x}\) approaches \(0\). Thus, the expression simplifies to:
\[
\lim_{x \rightarrow -\infty} \frac{3}{\sqrt{1 - 0}} = \frac{3}{\sqrt{1}} = 3
\]
However, since \( x \) is negative, we need to consider the sign of the square root:
\[
\sqrt{x^2 - x} \approx |x| \text{ for large } |x| \text{, which is } -x \text{ when } x \text{ is negative.}
\]
Thus, the limit becomes:
\[
\lim_{x \rightarrow -\infty} \frac{3x}{-x} = -3
\]
Final Answer
The limit exists and is given by:
\[
\boxed{-3}
\]