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Which exponential equation is equivalent to this logarithmic equation?
[tex]\[
\log _5 x - \log _5 25 = 7
\][/tex]

A. [tex]\(5^9 = x\)[/tex]

B. [tex]\(7^5 = x\)[/tex]

C. [tex]\(5^5 = x\)[/tex]

D. [tex]\(7^9 = x\)[/tex]


Sagot :

Let's solve the logarithmic equation step-by-step to find the equivalent exponential equation.

Given the logarithmic equation:
[tex]\[ \log_5 x - \log_5 25 = 7 \][/tex]

First, use the property of logarithms that allows you to combine the two logarithms on the left side:
[tex]\[ \log_5 \left(\frac{x}{25}\right) = 7 \][/tex]

Next, we need to convert the logarithmic equation to its exponential form. The general formula for converting a logarithmic equation [tex]\(\log_b (A) = C\)[/tex] to its exponential form is [tex]\(b^C = A\)[/tex].

In our case:
[tex]\[ \log_5 \left(\frac{x}{25}\right) = 7 \implies 5^7 = \frac{x}{25} \][/tex]

Now, solve for [tex]\(x\)[/tex]:
[tex]\[ 5^7 = \frac{x}{25} \][/tex]

Multiply both sides of the equation by 25 to isolate [tex]\(x\)[/tex]:
[tex]\[ 25 \cdot 5^7 = x \][/tex]

Simplify the right hand side:
[tex]\[ 25 \cdot 5^7 = 5^2 \cdot 5^7 = 5^{2+7} = 5^9 \][/tex]

Thus:
[tex]\[ 5^9 = x \][/tex]

Therefore, the correct exponential equation equivalent to the original logarithmic equation is:
[tex]\[ \boxed{5^9 = x} \][/tex]

The correct answer is:
A. [tex]\(5^9 = x\)[/tex]