1. **State the problem:** Solve the equation $\log_4(4x^2 + 7) - \log_4(x+1) = 2$ for $x$.
2. **Recall the logarithm subtraction rule:** $\log_b A - \log_b B = \log_b \left(\frac{A}{B}\right)$.
3. **Apply the rule:**
$$\log_4 \left(\frac{4x^2 + 7}{x+1}\right) = 2$$
4. **Rewrite the logarithmic equation in exponential form:**
$$\frac{4x^2 + 7}{x+1} = 4^2$$
5. **Calculate $4^2$:**
$$\frac{4x^2 + 7}{x+1} = 16$$
6. **Multiply both sides by $(x+1)$ to clear the denominator:**
$$\cancel{\frac{4x^2 + 7}{\cancel{x+1}}} \times \cancel{x+1} = 16(x+1)$$
$$4x^2 + 7 = 16x + 16$$
7. **Bring all terms to one side to form a quadratic equation:**
$$4x^2 + 7 - 16x - 16 = 0$$
$$4x^2 - 16x - 9 = 0$$
8. **Simplify the quadratic equation:**
$$4x^2 - 16x - 9 = 0$$
9. **Use the quadratic formula:**
$$x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}$$
where $a=4$, $b=-16$, and $c=-9$.
10. **Calculate the discriminant:**
$$b^2 - 4ac = (-16)^2 - 4 \times 4 \times (-9) = 256 + 144 = 400$$
11. **Calculate the roots:**
$$x = \frac{-(-16) \pm \sqrt{400}}{2 \times 4} = \frac{16 \pm 20}{8}$$
12. **Find the two possible solutions:**
- $$x = \frac{16 + 20}{8} = \frac{36}{8} = 4.5$$
- $$x = \frac{16 - 20}{8} = \frac{-4}{8} = -0.5$$
13. **Check for domain restrictions:**
- The argument of the logarithm must be positive.
- For $\log_4(4x^2 + 7)$, since $4x^2 + 7 > 0$ for all real $x$, no restriction here.
- For $\log_4(x+1)$, we need $x + 1 > 0 \Rightarrow x > -1$.
14. **Check solutions against domain:**
- $x=4.5$ satisfies $x > -1$.
- $x=-0.5$ also satisfies $x > -1$.
15. **Final answer:**
$$\boxed{x = 4.5 \text{ or } x = -0.5}$$
Logarithm Equation D02F72
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