1. **State the problem:** We want to find the value of the integral $$\int_2^4 f(x) g''(x) \, dx$$ given the values of $f(x)$, $g(x)$, $g'(x)$, and $g''(x)$ at $x=2$ and $x=4$, and that $f'(x) = 3$ for all $x$.
2. **Recall the integration by parts formula:**
$$\int u \, dv = uv - \int v \, du$$
We choose:
- $u = f(x)$ so that $du = f'(x) dx = 3 dx$
- $dv = g''(x) dx$ so that $v = g'(x)$
3. **Apply integration by parts:**
$$\int_2^4 f(x) g''(x) \, dx = \left[ f(x) g'(x) \right]_2^4 - \int_2^4 g'(x) f'(x) \, dx$$
4. **Evaluate the boundary term:**
$$\left[ f(x) g'(x) \right]_2^4 = f(4) g'(4) - f(2) g'(2) = 13 \times 7 - 7 \times 1 = 91 - 7 = 84$$
5. **Evaluate the remaining integral:**
Since $f'(x) = 3$ is constant,
$$\int_2^4 g'(x) f'(x) \, dx = 3 \int_2^4 g'(x) \, dx$$
6. **Use the Fundamental Theorem of Calculus:**
$$\int_2^4 g'(x) \, dx = g(4) - g(2) = 9 - 2 = 7$$
7. **Calculate the integral:**
$$3 \times 7 = 21$$
8. **Combine results:**
$$\int_2^4 f(x) g''(x) \, dx = 84 - 21 = 63$$
**Final answer:**
$$\boxed{63}$$
Integral By Parts Db19C5
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