Consider
\(f(x)=\frac{x}{x^2-4}\),
\(g(x)=\frac{4x}{x^2-4}\), and
\(h(x)=\frac{x^2+1}{x^2-4}\).
a) Find the common domain and the equations of the vertical asymptotes shared by all three functions.
b) Find \(f(3)\), \(g(3)\), \(h(3)\), \(f(0)\), \(g(0)\), and \(h(0)\).
c) Describe the transformation that maps the graph of \(f\) to the graph of \(g\).
d) Find the x-intercepts of each function.
Hints
- Factor the common denominator.
- A rational function is zero when its numerator is zero and its denominator is nonzero.
- Compare \(g(x)\) directly with \(f(x)\) to identify the transformation.
Solution
1. The common denominator factors as \((x-2)(x+2)\). No numerator cancels either factor, so the domain is \(\mathbb{R}\setminus\{-2, 2\}\), and the vertical asymptotes are \(x=-2\) and \(x=2\).
2. \(f(3)=\frac{3}{5}=0.6\), \(g(3)=\frac{12}{5}=2.4\), and \(h(3)=2\). Also, \(f(0)=0\), \(g(0)=0\), and \(h(0)=-\frac{1}{4}\).
3. Since \(g(x)=4f(x)\), the graph of \(g\) is a vertical stretch of the graph of \(f\) by a factor of \(4\).
4. The functions \(f\) and \(g\) have the x-intercept \((0, 0)\). The numerator \(x^2+1\) has no real zeros, so \(h\) has no x-intercepts.
Answer
a) Domain: \(\mathbb{R}\setminus\{-2, 2\}\); vertical asymptotes: \(x=-2\) and \(x=2\)
b) \(f(3)=0.6\), \(g(3)=2.4\), \(h(3)=2\); \(f(0)=0\), \(g(0)=0\), \(h(0)=-\frac{1}{4}\)
c) Vertical stretch by a factor of \(4\)
d) \(f\) and \(g\): \((0, 0)\); \(h\): no x-intercepts