Chapter 5: Problem 13
Write the expression as one logarithm. $$ \log \left(x^{3} y^{2}\right)-2 \log x \sqrt[3]{y}-3 \log \left(\frac{x}{y}\right) $$
Short Answer
Expert verified
\( \log \left( \frac{y^{13/3}}{x^2} \right) \)
Step by step solution
01
Apply the Power Rule of Logarithms
Recall that the power rule of logarithms states that \( a \log b = \log b^a \). Apply this rule to each term in the expression:\[2\log x \sqrt[3]{y} = \log (x\sqrt[3]{y})^2 = \log (x^2 y^{2/3}) \]\[3 \log \left(\frac{x}{y}\right) = \log \left(\frac{x}{y}\right)^3 = \log \left(\frac{x^3}{y^3}\right) \]The expression now becomes:\[\log (x^3 y^2) - \log (x^2 y^{2/3}) - \log \left(\frac{x^3}{y^3}\right)\]
02
Apply the Quotient Rule of Logarithms
The quotient rule of logarithms states that \( \log a - \log b = \log \frac{a}{b} \). Apply this rule to the modified expression:\[ \log \frac{x^3 y^2}{x^2 y^{2/3}} - \log \left(\frac{x^3}{y^3}\right) \]
03
Simplify the Expression
Simplify the expression within each logarithm by performing division and applying the laws of exponents:\[ \log \frac{x^3 y^2}{x^2 y^{2/3}} = \log \left( x^{3-2} y^{2-(2/3)} \right) = \log \left( x^1 y^{4/3} \right) \]Now substitute back into the expression:\[ \log (x y^{4/3}) - \log \left(\frac{x^3}{y^3}\right) \]
04
Combine the Logarithms Using the Quotient Rule Again
Combine the two logarithms using the quotient rule once more:\[ \log \frac{x y^{4/3}}{\frac{x^3}{y^3}} \]Perform division:\[ \frac{x y^{4/3} \cdot y^3}{x^3} = \frac{y^{4/3 + 3}}{x^{3-1}} = \frac{y^{13/3}}{x^2} \]
05
Final Step: Express as One Logarithm
The final expression simplifies to:\[ \log \left( \frac{y^{13/3}}{x^2} \right) \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Power Rule of Logarithms
The Power Rule of Logarithms is a fundamental tool in simplifying complex logarithmic expressions. This rule states that if you have an expression of the form \( a \log b \), you can rewrite it as \( \log b^a \). This is especially useful when dealing with logarithms involving exponents.
Imagine you have \( 2\log x \sqrt[3]{y} \). Using the power rule, this can be changed into \( \log (x \sqrt[3]{y})^2 \). This becomes \( \log (x^2 y^{2/3}) \) by applying the power inside the logarithm to both \( x \) and \( y \).
Imagine you have \( 2\log x \sqrt[3]{y} \). Using the power rule, this can be changed into \( \log (x \sqrt[3]{y})^2 \). This becomes \( \log (x^2 y^{2/3}) \) by applying the power inside the logarithm to both \( x \) and \( y \).
- It simplifies expressions by combining multiplication and exponentiation under a single logarithm.
- Keeps calculations tidy by reducing the number of operations you have to perform.
Quotient Rule of Logarithms
The Quotient Rule of Logarithms is a powerful mechanism for handling subtraction between logarithmic expressions. It is expressed by the formula \( \log a - \log b = \log \frac{a}{b} \). This allows a subtraction of logs to be combined into a single log.
In practice, consider the expression \( \log (x^3 y^2) - \log (x^2 y^{2/3}) \). We can apply the quotient rule to write it as \( \log \frac{x^3 y^2}{x^2 y^{2/3}} \).
In practice, consider the expression \( \log (x^3 y^2) - \log (x^2 y^{2/3}) \). We can apply the quotient rule to write it as \( \log \frac{x^3 y^2}{x^2 y^{2/3}} \).
- Useful for simplifying expressions, making them more compact.
- Transforms complex subtractive relationships in logs into division inside a single logarithm.
Laws of Exponents
The Laws of Exponents play a crucial role when handling expressions inside a logarithm, especially during simplification. These laws govern how we combine and manipulate powers of the same base.
In the context of logarithms, let's say you have \( \frac{x^3 y^2}{x^2 y^{2/3}} \). Here, you need to apply the laws such as:
In the context of logarithms, let's say you have \( \frac{x^3 y^2}{x^2 y^{2/3}} \). Here, you need to apply the laws such as:
- When dividing like bases, you subtract their exponents: \( x^{3-2} = x^1 \).
- When dealing with \( y \), \( y^{2-(2/3)} = y^{4/3} \).
Simplifying Logarithms
Simplifying logarithmic expressions involves applying rules systematically until you reach the simplest form possible. This means combining rules of logarithms and exponents to condense everything into a single, clear expression.
Take for instance transforming \( \log \frac{x y^{4/3}}{\frac{x^3}{y^3}} \) into a simplified form. By performing careful division, you manage to reorganize it to \( \frac{y^{13/3}}{x^2} \).
Take for instance transforming \( \log \frac{x y^{4/3}}{\frac{x^3}{y^3}} \) into a simplified form. By performing careful division, you manage to reorganize it to \( \frac{y^{13/3}}{x^2} \).
- Process includes employing exponent and log rules strategically.
- Ensures maximum reduction of expression complexity making further mathematical manipulation easier.