Ivt Root 93Bfa9
1. **Problem:** Use the Intermediate Value Theorem (IVT) to show that the function
$$f(x) = e^{x/4} + \frac{1}{8}x^2 - 4$$
has a root in the interval $[0,4]$.
2. **Recall the Intermediate Value Theorem:**
If a function $f$ is continuous on a closed interval $[a,b]$ and $f(a)$ and $f(b)$ have opposite signs, then there exists at least one $c \in (a,b)$ such that $f(c) = 0$.
3. **Check continuity:**
The function $f(x)$ is composed of exponential and polynomial terms, both continuous everywhere, so $f$ is continuous on $[0,4]$.
4. **Evaluate $f(0)$:**
$$f(0) = e^{0/4} + \frac{1}{8} \cdot 0^2 - 4 = 1 + 0 - 4 = -3$$
5. **Evaluate $f(4)$:**
$$f(4) = e^{4/4} + \frac{1}{8} \cdot 4^2 - 4 = e^{1} + \frac{1}{8} \cdot 16 - 4 = e + 2 - 4 = e - 2$$
Using $e \approx 2.718$,
$$f(4) \approx 2.718 - 2 = 0.718 > 0$$
6. **Sign check:**
At $x=0$, $f(0) = -3 < 0$ and at $x=4$, $f(4) \approx 0.718 > 0$.
7. **Conclusion:**
Since $f$ is continuous on $[0,4]$ and $f(0)$ and $f(4)$ have opposite signs, by the Intermediate Value Theorem, there exists some $c \in (0,4)$ such that
$$f(c) = 0$$
which means $f$ has at least one root in $[0,4]$.
**Final answer:** There is at least one root of $f(x)$ in the interval $[0,4]$ by the Intermediate Value Theorem.