Find A B 2Eb4D3
1. **State the problem:** We have a function $$y = -x^2 + 2(\log(2)a)x + \log(2)b$$ defined for $$0 \leq x \leq 4$$. The maximum value of the function is 5 and the minimum value is -4. We need to find the values of $$a$$ and $$b$$.
2. **Identify the type of function:** This is a quadratic function in the form $$y = ax^2 + bx + c$$ where $$a = -1$$, $$b = 2(\log(2)a)$$, and $$c = \log(2)b$$.
3. **Find the vertex:** The vertex of a quadratic $$y = ax^2 + bx + c$$ is at $$x = -\frac{b}{2a}$$.
Here, $$x_v = -\frac{2(\log(2)a)}{2(-1)} = \log(2)a$$.
4. **Calculate the vertex value:** Substitute $$x_v$$ into the function:
$$$y_v = - (\log(2)a)^2 + 2(\log(2)a)(\log(2)a) + \log(2)b = - (\log(2)a)^2 + 2(\log(2)a)^2 + \log(2)b = (\log(2)a)^2 + \log(2)b$$$
5. **Determine max and min values:** Since $$a = -1 < 0$$, the parabola opens downward, so the vertex is a maximum point.
Given max value $$y_v = 5$$, so:
$$$(\log(2)a)^2 + \log(2)b = 5$$$
6. **Check values at endpoints:** The minimum value is -4, which must occur at one of the endpoints $$x=0$$ or $$x=4$$.
At $$x=0$$:
$$$y = -0 + 0 + \log(2)b = \log(2)b$$$
At $$x=4$$:
$$$y = -16 + 8(\log(2)a) + \log(2)b$$$
7. **Set minimum value:** The minimum is -4, so either:
- $$\log(2)b = -4$$ or
- $$-16 + 8(\log(2)a) + \log(2)b = -4$$
8. **Solve system:** From step 5:
$$$(\log(2)a)^2 + \log(2)b = 5$$
If minimum at $$x=0$$:
$$\log(2)b = -4$$
Substitute into max equation:
$$(\log(2)a)^2 - 4 = 5 \Rightarrow (\log(2)a)^2 = 9 \Rightarrow \log(2)a = \pm 3$$
If minimum at $$x=4$$:
$$-16 + 8(\log(2)a) + \log(2)b = -4 \Rightarrow 8(\log(2)a) + \log(2)b = 12$$
Using max equation:
$$(\log(2)a)^2 + \log(2)b = 5$$
Subtracting these two:
$$8(\log(2)a) + \log(2)b - ((\log(2)a)^2 + \log(2)b) = 12 - 5$$
$$8(\log(2)a) - (\log(2)a)^2 = 7$$
Rewrite:
$$(\log(2)a)^2 - 8(\log(2)a) + 7 = 0$$
Solve quadratic:
$$\log(2)a = \frac{8 \pm \sqrt{64 - 28}}{2} = \frac{8 \pm \sqrt{36}}{2} = \frac{8 \pm 6}{2}$$
So:
$$\log(2)a = 7 \text{ or } 1$$
Use max equation to find $$\log(2)b$$:
- For $$\log(2)a = 7$$:
$$(7)^2 + \log(2)b = 5 \Rightarrow 49 + \log(2)b = 5 \Rightarrow \log(2)b = -44$$
- For $$\log(2)a = 1$$:
$$(1)^2 + \log(2)b = 5 \Rightarrow 1 + \log(2)b = 5 \Rightarrow \log(2)b = 4$$
9. **Summary of solutions:**
- Case 1 (min at $$x=0$$): $$\log(2)a = \pm 3$$, $$\log(2)b = -4$$
- Case 2 (min at $$x=4$$): $$\log(2)a = 7$$, $$\log(2)b = -44$$ or $$\log(2)a = 1$$, $$\log(2)b = 4$$
10. **Find $$a$$ and $$b$$:** Recall $$\log(2)a = \log_2 a$$, so:
$$a = 2^{\log(2)a}$$ and $$b = 2^{\log(2)b}$$.
For example, for $$\log(2)a = 3$$, $$a = 2^3 = 8$$.
**Final answers:**
- If minimum at $$x=0$$: $$a = 2^{\pm 3} = 8 \text{ or } \frac{1}{8}$$, $$b = 2^{-4} = \frac{1}{16}$$
- If minimum at $$x=4$$:
- $$a = 2^7 = 128$$, $$b = 2^{-44}$$ (very small)
- $$a = 2^1 = 2$$, $$b = 2^4 = 16$$