1. **Problem Statement:**
Evaluate the definite integrals of the piecewise linear function $f(x)$ given the graph description:
- $f(x)=0$ from $x=0$ to $x=2$
- At $x=3$, $f(3)=1$
- $f(x)$ increases linearly from $(3,1)$ to $(10,3)$
We need to find:
(a) $\int_0^3 f(x) \, dx$
(b) $\int_3^4 f(x) \, dx$
(c) $\int_0^4 f(x) \, dx$
(d) $\int_4^{10} f(x) \, dx$
(e) $\int_0^{10} -4 f(x) \, dx$
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2. **Step 1: Understand the function and geometry**
- From $0$ to $2$, $f(x)=0$, so area under curve is zero.
- At $x=3$, $f(3)=1$.
- From $3$ to $10$, $f(x)$ is linear from $1$ to $3$.
3. **Step 2: Calculate $\int_0^3 f(x) \, dx$**
- From $0$ to $2$, $f(x)=0$, so area is $0$.
- From $2$ to $3$, the graph jumps from $0$ to $1$ at $x=3$.
- Since no value is given between $2$ and $3$, assume $f(x)=0$ for $2 \leq x < 3$ (based on description).
- So area from $0$ to $3$ is $0$.
4. **Step 3: Calculate $\int_3^4 f(x) \, dx$**
- From $3$ to $10$, $f(x)$ is linear from $1$ to $3$.
- Find equation of line between $(3,1)$ and $(10,3)$:
$$m=\frac{3-1}{10-3}=\frac{2}{7}$$
$$f(x)=1 + \frac{2}{7}(x-3)$$
- Evaluate integral from $3$ to $4$:
$$\int_3^4 \left(1 + \frac{2}{7}(x-3)\right) dx = \int_3^4 1 \, dx + \int_3^4 \frac{2}{7}(x-3) \, dx$$
Calculate each:
$$\int_3^4 1 \, dx = 4-3=1$$
$$\int_3^4 \frac{2}{7}(x-3) \, dx = \frac{2}{7} \int_3^4 (x-3) \, dx = \frac{2}{7} \left[ \frac{(x-3)^2}{2} \right]_3^4 = \frac{2}{7} \times \frac{(4-3)^2 - 0}{2} = \frac{2}{7} \times \frac{1}{2} = \frac{1}{7}$$
Sum:
$$1 + \frac{1}{7} = \frac{8}{7} \approx 1.1429$$
5. **Step 4: Calculate $\int_0^4 f(x) \, dx$**
- This is sum of $\int_0^3 f(x) \, dx$ and $\int_3^4 f(x) \, dx$:
$$0 + \frac{8}{7} = \frac{8}{7}$$
6. **Step 5: Calculate $\int_4^{10} f(x) \, dx$**
- Use the same linear function:
$$\int_4^{10} \left(1 + \frac{2}{7}(x-3)\right) dx = \int_4^{10} 1 \, dx + \int_4^{10} \frac{2}{7}(x-3) \, dx$$
Calculate each:
$$\int_4^{10} 1 \, dx = 10-4=6$$
$$\int_4^{10} \frac{2}{7}(x-3) \, dx = \frac{2}{7} \left[ \frac{(x-3)^2}{2} \right]_4^{10} = \frac{2}{7} \times \frac{(10-3)^2 - (4-3)^2}{2} = \frac{2}{7} \times \frac{49 - 1}{2} = \frac{2}{7} \times 24 = \frac{48}{7}$$
Sum:
$$6 + \frac{48}{7} = \frac{42}{7} + \frac{48}{7} = \frac{90}{7} \approx 12.8571$$
7. **Step 6: Calculate $\int_0^{10} -4 f(x) \, dx$**
- Use linearity of integral:
$$\int_0^{10} -4 f(x) \, dx = -4 \int_0^{10} f(x) \, dx$$
- Calculate $\int_0^{10} f(x) \, dx = \int_0^3 f(x) \, dx + \int_3^{10} f(x) \, dx = 0 + \int_3^{10} f(x) \, dx$
- Calculate $\int_3^{10} f(x) \, dx$:
$$\int_3^{10} \left(1 + \frac{2}{7}(x-3)\right) dx = \int_3^{10} 1 \, dx + \int_3^{10} \frac{2}{7}(x-3) \, dx = 7 + \frac{2}{7} \times \frac{(10-3)^2 - 0}{2} = 7 + \frac{2}{7} \times \frac{49}{2} = 7 + 7 = 14$$
- So:
$$\int_0^{10} -4 f(x) \, dx = -4 \times 14 = -56$$
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**Final answers:**
(a) $0$
(b) $\frac{8}{7}$
(c) $\frac{8}{7}$
(d) $\frac{90}{7}$
(e) $-56$
Definite Integrals De3Ff7
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