1. The problem states that the graph of the second derivative $f''$ of a continuous function $f$ is given on the interval $[0,9]$, and $f$ has only one critical point at $x=6$.
2. Recall that a critical point of $f$ occurs where the first derivative $f'$ is zero or undefined. Here, $x=6$ is the only critical point.
3. To classify the critical point, we use the second derivative test:
$$\text{If } f''(x) > 0, \text{ then } f \text{ is concave up and } f \text{ has a relative minimum at } x.$$
$$\text{If } f''(x) < 0, \text{ then } f \text{ is concave down and } f \text{ has a relative maximum at } x.$$
4. From the graph of $f''$, at $x=6$, $f''(6) > 0$ (the graph is above the $x$-axis), so $f$ is concave up at $x=6$.
5. Therefore, $f$ has a relative minimum at $x=6$.
6. To determine if this is an absolute minimum, consider the behavior of $f''$ and $f'$ on the interval:
- Since $x=6$ is the only critical point, $f'$ changes sign only there.
- The concavity changes and the shape of $f''$ suggest $f$ decreases before $6$ and increases after $6$, consistent with a relative minimum.
- However, without information about $f$ at the endpoints, we cannot confirm if this minimum is absolute.
7. Hence, the correct statement is:
(A) $f$ has a relative minimum at $x=6$ but not an absolute minimum.
Final answer: (A)
Second Derivative Test Dd166C
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