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Solve [tex]$9^{x+4}=11$[/tex] for [tex]$x$[/tex] using the change of base formula [tex]$\log _b y=\frac{\log y}{\log b}$[/tex].

A. [tex]-3.094[/tex]
B. [tex]-2.909[/tex]
C. [tex]4.916[/tex]
D. [tex]5.091[/tex]


Sagot :

To solve the equation [tex]\(9^{x+4} = 11\)[/tex], we will use logarithms to simplify and solve for [tex]\(x\)[/tex]. Follow these steps:

1. Apply the logarithm to both sides of the equation:
[tex]\[ \log(9^{x+4}) = \log(11) \][/tex]

2. Use the power rule of logarithms which states [tex]\(\log(a^b) = b \log(a)\)[/tex]:
[tex]\[ (x+4) \log(9) = \log(11) \][/tex]

3. Isolate the term involving [tex]\(x\)[/tex]:
[tex]\[ x + 4 = \frac{\log(11)}{\log(9)} \][/tex]

4. Calculate the right-hand side:
[tex]\(\log(11)\)[/tex] and [tex]\(\log(9)\)[/tex] are standard logarithms which can be calculated using a calculator; the precise values of [tex]\(\log(11)\)[/tex] and [tex]\(\log(9)\)[/tex] are:
[tex]\[ \log(11) \approx 1.041393 \][/tex]
[tex]\[ \log(9) \approx 0.954243 \][/tex]

So,
[tex]\[ \frac{\log(11)}{\log(9)} \approx \frac{1.041393}{0.954243} \approx 1.091329 \][/tex]

5. To isolate [tex]\(x\)[/tex], subtract 4 from both sides:
[tex]\[ x = 1.091329 - 4 \][/tex]
[tex]\[ x \approx -2.908671 \][/tex]

Now, we need to compare this solution with the given potential answers to determine the closest one. The possible answers are:

- [tex]\(-3.094\)[/tex]
- [tex]\(-2.909\)[/tex]
- [tex]\(4.916\)[/tex]
- [tex]\(5.091\)[/tex]

The solution we found is approximately [tex]\(-2.908671\)[/tex]. Among the choices, the closest to [tex]\(-2.908671\)[/tex] is [tex]\(-2.909\)[/tex].

Therefore, the nearest solution to [tex]\(x\)[/tex] is:
[tex]\[ \boxed{-2.909} \][/tex]