1. **State the problem:** Find all relative maxima and minima of the function $g$ given its derivative $g'(x)$.
2. **Recall the critical points:** Critical points occur where $g'(x) = 0$ or $g'(x)$ is undefined.
3. **Use the first derivative test:** If $g'(x)$ changes from positive to negative at a critical point, $g$ has a relative maximum there.
If $g'(x)$ changes from negative to positive, $g$ has a relative minimum.
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### Problem 4: $g'(x) = (x + 4)e^x$
4.1. Find critical points by solving $g'(x) = 0$:
$$
(x + 4)e^x = 0
$$
Since $e^x > 0$ for all $x$, we have:
$$
x + 4 = 0 \implies x = -4
$$
4.2. Test intervals around $x = -4$:
- For $x < -4$, say $x = -5$, $g'(-5) = (-5 + 4)e^{-5} = (-1)(positive) = negative$
- For $x > -4$, say $x = 0$, $g'(0) = (0 + 4)e^0 = 4(1) = positive$
4.3. Since $g'(x)$ changes from negative to positive at $x = -4$, $g$ has a **relative minimum** at $x = -4$.
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### Problem 5: $g'(x) = x^2 + 5x + 4$
5.1. Factor the quadratic:
$$
g'(x) = (x + 4)(x + 1)
$$
5.2. Find critical points by solving $g'(x) = 0$:
$$
(x + 4)(x + 1) = 0 \implies x = -4, -1
$$
5.3. Test intervals around $x = -4$ and $x = -1$:
- For $x < -4$, say $x = -5$, $g'(-5) = (-5 + 4)(-5 + 1) = (-1)(-4) = positive$
- For $-4 < x < -1$, say $x = -2$, $g'(-2) = (-2 + 4)(-2 + 1) = (2)(-1) = negative$
- For $x > -1$, say $x = 0$, $g'(0) = (0 + 4)(0 + 1) = 4(1) = positive$
5.4. At $x = -4$, $g'(x)$ changes from positive to negative, so $g$ has a **relative maximum** at $x = -4$.
5.5. At $x = -1$, $g'(x)$ changes from negative to positive, so $g$ has a **relative minimum** at $x = -1$.
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**Final answers:**
- Problem 4: Relative minimum at $x = -4$.
- Problem 5: Relative maximum at $x = -4$, relative minimum at $x = -1$.
Relative Extrema 1914Ae
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