For each condition, give two different choices of exponents \(n\) and \(m\) from \(\{1, 2, 3, 4, 5, 6\}\) and a constant \(c \in \mathbb{R}\) so that \(f(x) = x^n + 5x^m + c\) satisfies the condition.
a) The graph of \(f\) is symmetric about the y-axis.
b) The graph of \(f\) is symmetric about the origin.
Hints
- Determine whether each symmetry condition requires even powers or odd powers.
- Treat the constant \(c\) as the term \(cx^0\).
- Decide whether a vertical shift is compatible with symmetry about the origin.
Solution
1. For symmetry about the y-axis, \(f\) must be even. Therefore, \(n\) and \(m\) must both be even. The constant \(c\) may be any real number. Two examples are \((n, m, c) = (2, 4, 3)\) and \((6, 2, 0)\).
2. For symmetry about the origin, \(f\) must be odd. Therefore, \(n\) and \(m\) must both be odd, and the constant term must be zero. Two examples are \((n, m, c) = (1, 3, 0)\) and \((5, 1, 0)\).
Answer
a) Sample answers: \((n, m, c) = (2, 4, 3)\) and \((6, 2, 0)\). In general, \(n, m \in \{2, 4, 6\}\) and \(c \in \mathbb{R}\).
b) Sample answers: \((n, m, c) = (1, 3, 0)\) and \((5, 1, 0)\). In general, \(n, m \in \{1, 3, 5\}\) and \(c = 0\).