53243412
Panel a) shows the graphs of \(f_1\) (blue) and \(f_2\) (orange). Panel b) shows two possible derivative graphs, \(p\) (green) and \(q\) (purple).
a) Match each function, \(f_1\) and \(f_2\), with its derivative, \(p\) or \(q\). Justify your choices.
b) On the displayed interval \([-3.5, 3.5]\), find the intervals where \(f_1\) is strictly increasing and strictly decreasing.
Hints
- Match the zeros of a derivative with the horizontal tangents of its function.
- Compare the sign of each possible derivative with where the function increases or decreases.
- Use the critical \(x\)-values as interval endpoints.
Solution
1. The graph of \(f_1\) has a local maximum at \(x = -2\) and a local minimum at \(x = 2\), so its derivative must be zero at those values.
2. Between the two critical points, \(f_1\) decreases, so its derivative must be negative there. Graph \(p\) is negative between its zeros, while graph \(q\) is positive. Therefore, \(f_1' = p\) and \(f_2' = q\).
3. Graph \(p\) is positive on \([-3.5, -2)\) and \((2, 3.5]\), and negative on \((-2, 2)\). Thus, \(f_1\) is strictly increasing on \([-3.5, -2]\) and \([2, 3.5]\), and strictly decreasing on \([-2, 2]\).
Answer
a) \(f_1 \rightarrow p\) and \(f_2 \rightarrow q\)
b) Increasing on \([-3.5, -2]\) and \([2, 3.5]\); decreasing on \([-2, 2]\).
