52194112
Consider the rational function \(f(x)=3x+1-\frac{2}{x+4}\).
Give the equation of the slant asymptote. Then describe the graph's end behavior as \(x\to\infty\) and as \(x\to-\infty\), including whether the graph approaches the asymptote from above or below.
Hints
- Which part of the function approaches \(0\) as \(|x|\) becomes large?
- How does a line with positive slope behave as \(x\to\infty\) and as \(x\to-\infty\)?
- Check the sign of the fractional term for large positive and negative values of \(x\).
Solution
1. Since \(\frac{2}{x+4}\to 0\) as \(x\to\pm\infty\), the slant asymptote is \(y=3x+1\).
2. As \(x\to\infty\), \(f(x)\to\infty\). Because \(\frac{2}{x+4}>0\) for large positive \(x\), \(f(x)<3x+1\), so the graph approaches the asymptote from below.
3. As \(x\to-\infty\), \(f(x)\to-\infty\). Because \(\frac{2}{x+4}<0\) for large negative \(x\), \(f(x)>3x+1\), so the graph approaches the asymptote from above.
Answer
The slant asymptote is \(y=3x+1\).
As \(x\to\infty\), \(f(x)\to\infty\), and the graph approaches the asymptote from below.
As \(x\to-\infty\), \(f(x)\to-\infty\), and the graph approaches the asymptote from above.
