Consider the functions \(f(x)=\frac{1-4x}{2x+6}\), \(g(x)=\frac{x^2+1}{x-1}\), and \(h(x)=\frac{3x-2}{x^2+2}\).
Determine whether each statement is true or false. Justify your answers.
a) The x-axis is a horizontal asymptote of the graph of \(h\).
b) The graph of \(g\) has the slant asymptote \(y=x+1\).
c) The graphs of \(f\) and \(h\) have the same total number of horizontal, slant, and vertical asymptotes.
d) As \(x\to\infty\), all three functions have the same limiting behavior.
Hints
- Analyze each function separately.
- Check excluded values when looking for vertical asymptotes.
- Use polynomial division when the numerator's degree is one greater than the denominator's degree.
- Compare the leading terms to determine end behavior.
Solution
1. For \(h\), the denominator has greater degree than the numerator, so \(h(x)\to 0\) as \(x\to\infty\). Thus, a) is true.
2. Polynomial division gives \(g(x)=x+1+\frac{2}{x-1}\). Therefore, \(y=x+1\) is the slant asymptote, so b) is true.
3. The graph of \(f\) has a vertical asymptote at \(x=-3\) and a horizontal asymptote at \(y=-2\), for a total of two. Since \(x^2+2>0\) for all real \(x\), \(h\) has no vertical asymptote and has only the horizontal asymptote \(y=0\). Therefore, c) is false.
4. As \(x\to\infty\), \(f(x)\to-2\), \(g(x)\to\infty\), and \(h(x)\to 0\). Therefore, d) is false.
Answer
a) True
b) True
c) False; \(f\) has two asymptotes, while \(h\) has one.
d) False; as \(x\to\infty\), \(f(x)\to-2\), \(g(x)\to\infty\), and \(h(x)\to 0\).