Chapter 5: Problem 69
Use the properties of logarithms to rewrite each logarithm if possible. Assume that all variables represent positive real numbers. $$\log _{5} \frac{5 \sqrt{7}}{3 m}$$
Short Answer
Expert verified
\( 1 + \frac{1}{2} \log_5 7 - \log_5 3 - \log_5 m \)
Step by step solution
01
Apply the Quotient Rule
The Quotient Rule of logarithms states that \( \log_b \left( \frac{x}{y} \right) = \log_b x - \log_b y \). We apply this rule to \( \log_5 \left( \frac{5 \sqrt{7}}{3m} \right) \): \[ \log_5 \left( \frac{5 \sqrt{7}}{3m} \right) = \log_5 (5 \sqrt{7}) - \log_5 (3m) \]
02
Apply the Product Rule
The Product Rule of logarithms is \( \log_b (xy) = \log_b x + \log_b y \). We apply it to \( \log_5 (5 \sqrt{7}) \): \[ \log_5 (5 \sqrt{7}) = \log_5 5 + \log_5 \sqrt{7} \]
03
Simplify using the logarithm of a power
The logarithm \( \log_5 5 = 1 \) because any logarithm of its own base is 1. Also, rewrite \( \log_5 \sqrt{7} \) using the power rule: \[ \sqrt{7} = 7^{1/2}, \text{ so } \log_5 \sqrt{7} = \log_5 (7^{1/2}) = \frac{1}{2} \log_5 7 \] Thus, \[ \log_5 (5 \sqrt{7}) = 1 + \frac{1}{2} \log_5 7 \]
04
Apply the Product Rule to the denominator
Apply the Product Rule to the denominator term \( \log_5 (3m) \), breaking it into two separate logarithms: \[ \log_5 (3m) = \log_5 3 + \log_5 m \]
05
Combine all parts
Combine the results from previous steps. Use the equation from Step 1 and substitute the results from Step 2 and Step 4: \[ \log_5 \left( \frac{5 \sqrt{7}}{3m} \right) = (1 + \frac{1}{2} \log_5 7) - (\log_5 3 + \log_5 m) \] Simplifying gives: \[ \log_5 \left( \frac{5 \sqrt{7}}{3m} \right) = 1 + \frac{1}{2} \log_5 7 - \log_5 3 - \log_5 m \]
06
Final expression
The final expression, using the properties of logarithms, is: \[ 1 + \frac{1}{2} \log_5 7 - \log_5 3 - \log_5 m \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Quotient Rule
The quotient rule in logarithms helps us decompose a logarithm of a fraction into a subtraction of two logs. It's a valuable tool when you're working with expressions that involve division inside a logarithm. Here's how it works: if you have a logarithm of a fraction like \( \log_b \left( \frac{x}{y} \right) \), you can split it into two parts: \( \log_b x - \log_b y \). In practice, this means you can
- change a complex division problem into simpler subtraction problems,
- making it easier to solve or simplify the expression efficiently.
Product Rule
The product rule of logarithms is a handy property for breaking down logs of products into sums of logs. The rule states that for any logarithm \( \log_b (xy) = \log_b x + \log_b y \). This is useful because
- we can break down a complex multiplication inside a logarithm into simpler addition expressions,
- facilitating the step-by-step simplification or calculation process.
Logarithm Properties
Logarithm properties encompass various rules that help in simplifying and solving logarithmic expressions. Some crucial properties include:
- The identity \( \log_b b = 1 \), where any log that has the same base and argument equals 1.
- Using log transformations for powers and radicals which are explained by the power rule.
Logarithm of a Power
Logarithms of powers can be simplified using the power rule. This rule says \( \log_b (x^a) = a \cdot \log_b x \), which means you can take the exponent and place it as a multiplier in front of the logarithm.For instance,
- if you have a square root like \( \sqrt{7} \), this is the same as \( 7^{1/2} \).
- Applying the power rule, \( \log_5 \sqrt{7} \) becomes \( \frac{1}{2} \log_5 7 \).