1. **Problem statement:** We have a function $f$ defined graphically on $[-10,10]$ with line segments and a quarter circle. The function $g$ is defined as
$$g(x) = \int_1^x f(t) \, dt.$$
We need to find all intervals on $[-9,9]$ where $g$ is concave down.
2. **Recall the relationship between $g$ and $f$:**
Since $g(x) = \int_1^x f(t) \, dt$, by the Fundamental Theorem of Calculus,
$$g'(x) = f(x).$$
3. **Concavity and second derivative:**
The concavity of $g$ depends on the sign of $g''(x)$:
- If $g''(x) < 0$, then $g$ is concave down.
- If $g''(x) > 0$, then $g$ is concave up.
Since $g'(x) = f(x)$, then
$$g''(x) = f'(x).$$
4. **Interpretation:**
To find where $g$ is concave down, we need to find where $f'(x) < 0$ on $[-9,9]$.
5. **Analyze $f$ on $[-9,9]$ using the graph segments:**
- From $-9$ to $-6$: $f$ is on the line segment from $(-10,0)$ to $(-6,6)$, which is increasing (slope positive).
- From $-6$ to $-1$: $f$ goes from $( -6,6)$ to $(-1,0)$, which is decreasing (slope negative).
- From $-1$ to $1$: $f$ is constant at $0$ (slope zero).
- From $1$ to $3$: $f$ goes from $(1,0)$ to $(3,4)$, increasing (slope positive).
- From $3$ to $5$: $f$ goes from $(3,4)$ to $(5,-5)$, decreasing (slope negative).
- From $5$ to $7$: $f$ goes from $(5,-5)$ to $(7,3)$, increasing (slope positive).
- From $7$ to $9$: $f$ follows a quarter circle arc from $(7,3)$ to $(9,5)$, which is concave down but we need the slope of $f$ (derivative of $f$). The quarter circle is the top-right quarter of a circle rising, so the slope $f'(x)$ is decreasing (negative) because the circle's slope decreases as $x$ increases in this arc.
6. **Summarize intervals where $f'(x) < 0$ (i.e., $g$ concave down):**
- $(-6,-1)$: $f$ decreasing
- $(3,5)$: $f$ decreasing
- $(7,9)$: slope of $f$ decreasing on quarter circle arc
7. **Final answer:**
$$\boxed{\text{The function } g \text{ is concave down on } [-9,9] \text{ precisely on the intervals } (-6,-1), (3,5), \text{ and } (7,9).}$$
Concavity Intervals 16Da28
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