51009711
Which function has a graph that is symmetric about the origin?
a) \(y = x(4 - x^2)\)
b) \(y = x(4 - x)\)
c) \(y = (4 - x)(4 + x)\)
d) \(y = x(4 - x)^2\)
Hints
- Recall the equation that defines an odd function.
- Expand each expression and examine the powers of \(x\).
- You can also compare the function values at \(x = 1\) and \(x = -1\).
Solution
1. A graph is symmetric about the origin when its function is odd, so \(f(-x) = -f(x)\).
2. For a), \(f(x) = x(4 - x^2) = 4x - x^3\). Both terms have odd powers, so \(f(-x) = -f(x)\).
3. For b), \(f(x) = 4x - x^2\), which contains both odd and even powers.
4. For c), \(f(x) = 16 - x^2\), which is even and is symmetric about the y-axis.
5. For d), \(f(x) = 16x - 8x^2 + x^3\), which contains both odd and even powers.
Answer
a) \(y = x(4 - x^2)\)
