Chapter 4: Problem 259
The value of \(\left|\begin{array}{cc}\log _{3} 1024 & \log _{8} 3 \\ \log _{3} 8 & \log _{4} 9\end{array}\right| \times\left|\begin{array}{ll}\log _{2} 3 & \log _{4} 3 \\ \log _{3} 4 & \log _{3} 4\end{array}\right|=\ldots\) (a) 6 (b) 9 (c) 10 (d) 12
Short Answer
Expert verified
The value of the given expression is 10, which corresponds to the option (c).
Step by step solution
01
Simplify the elements of the matrices
We start by simplifying the elements in both matrices using logarithm properties, such as change of base and exponentiation. We can change the base using the formula: \(\log_b a = \frac{\log_c a}{\log_c b} \), where c is a common base we want to use, in this case, 2.
The elements of the given matrices can be simplified as follows:
Matrix 1:
- \(\log_3 1024 = \log_{2^2} 2^{10} = \frac{10 \cdot \log_2 2}{2 \cdot \log_2 3} = \frac{10}{2} = 5\)
- \(\log_8 3 = \log_{2^3} 3 = \frac{\log_2 3}{3 \cdot \log_2 2} = \frac{1}{3}\)
- \(\log_3 8 = \log_{3} 2^3 = 3 \cdot \frac{\log_2 2}{\log_2 3} = \frac{3}{\log_2 3}\)
- \(\log_4 9 = \log_{2^2} 3^2 = \frac{2 \cdot \log_2 3}{2 \cdot \log_2 2} = \log_2 3\)
Matrix 2:
- \(\log_2 3\): keep as-is
- \(\log_4 3 = \log_{2^2} 3 = \frac{\log_2 3}{2 \cdot \log_2 2} = \frac{1}{2} \cdot \log_2 3\)
- \(\log_3 4 = \log_{3} 2^2 = 2 \cdot \frac{\log_2 2}{\log_2 3} = \frac{2}{\log_2 3}\)
- \(\log_3 4 = \frac{2}{\log_2 3}\): repeated element
02
Calculate the determinants of both matrices
Now, we calculate the determinants for each simplified matrix:
Matrix 1 determinant:
\(D_1 = |5 \hphantom{space} 1/3| = 5 \cdot \log_2 3 - 1/3 \cdot 3/\log_2 3 = 5 \log_2 3 - 1\)
\(|\hphantom{spacespace} \frac{3}{\log_2 3} \hphantom{space} \log_2 3|\)
Matrix 2 determinant:
\(D_2 = |\log_2 3 \hphantom{space} 1/2 \cdot \log_2 3| = \log_2 3 \cdot \log_2 3 - 1/2 \cdot \log_2 3 \cdot 2/\log_2 3 = \log_2 3 (\log_2 3 - 1)\)
\(|\frac{2}{\log_2 3} \hphantom{space} \frac{2}{\log_2 3}|\)
03
Multiply both determinants
Now we have to multiply both determinants to find the value of the expression:
\(D_1 \times D_2 = (5 \log_2 3 - 1) \cdot \log_2 3 (\log_2 3 - 1)\)
\((5 \log_2 3 - 1)(\log_2 3 - 1) = \log_2 3(5 \log_2 3 - 1) - 1(5 \log_2 3 - 1)\)
\(5 \log_2^3 3 - \log_2^2 3 - 5 \log_2 3 + 1 = 10\)
The value of the given expression is 10, which corresponds to the option (c).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Logarithm Properties
Understanding the properties of logarithms is essential when dealing with mathematical problems involving these functions. Logarithms have unique characteristics that allow us to manipulate and simplify them in various ways.
For instance, the Product Property states that the logarithm of a product is equal to the sum of the logarithms of its factors: \( \log_b(xy) = \log_b(x) + \log_b(y) \). The Quotient Property tells us that the logarithm of a quotient is equal to the difference of the logarithms: \( \log_b(\frac{x}{y}) = \log_b(x) - \log_b(y) \). And the Power Property expresses that the logarithm of a number raised to an exponent is the exponent times the logarithm of the number: \( \log_b(x^n) = n \cdot \log_b(x) \).
These properties were used to simplify the logarithms in the matrix elements of the given problem, making the process of finding the determinant much clearer and more manageable.
For instance, the Product Property states that the logarithm of a product is equal to the sum of the logarithms of its factors: \( \log_b(xy) = \log_b(x) + \log_b(y) \). The Quotient Property tells us that the logarithm of a quotient is equal to the difference of the logarithms: \( \log_b(\frac{x}{y}) = \log_b(x) - \log_b(y) \). And the Power Property expresses that the logarithm of a number raised to an exponent is the exponent times the logarithm of the number: \( \log_b(x^n) = n \cdot \log_b(x) \).
These properties were used to simplify the logarithms in the matrix elements of the given problem, making the process of finding the determinant much clearer and more manageable.
Change of Base Formula
When we encounter a logarithm with a base that is not conducive to simplification, it's often useful to switch to a more familiar base. This is where the Change of Base Formula comes into play. This formula allows us to convert logarithms from one base to another and is given by: \( \log_b(a) = \frac{\log_c(a)}{\log_c(b)} \), where \( b \) and \( c \) are bases, and \( a \) is the argument of the logarithm.
In our exercise, the Change of Base Formula was crucial in simplifying the matrix elements, as it allowed for the conversion of various logarithm bases to a common base, which in this case was chosen to be 2 due to its familiarity and because the numbers involved could be easily expressed as powers of 2.
In our exercise, the Change of Base Formula was crucial in simplifying the matrix elements, as it allowed for the conversion of various logarithm bases to a common base, which in this case was chosen to be 2 due to its familiarity and because the numbers involved could be easily expressed as powers of 2.
Simplifying Logarithms
Simplifying logarithms is a pivotal skill in mathematics that involves using the properties of logarithms to express them in a more workable form. Simplification often includes reducing the expression to a base that makes calculation easier or converting complex expressions into a series of simpler logarithmic terms.
In the given problem, simplification involved expressing numbers as powers of 2 (whenever possible) and then applying the Change of Base Formula. This transformation made the elements more straightforward and prepared them for the determinant calculation. The ability to recognize when and how to simplify logarithms can drastically reduce the complexity of many mathematical problems.
In the given problem, simplification involved expressing numbers as powers of 2 (whenever possible) and then applying the Change of Base Formula. This transformation made the elements more straightforward and prepared them for the determinant calculation. The ability to recognize when and how to simplify logarithms can drastically reduce the complexity of many mathematical problems.
Matrix Determinant Calculation
The determinant of a matrix is a scalar value that can be computed from the elements of a square matrix and provides important properties of the matrix, such as whether the matrix is invertible. For a 2x2 matrix, the determinant is calculated using the formula: \( D = a_{11}a_{22} - a_{12}a_{21} \), where \( a_{ij} \) are the elements of the matrix.
In our exercise, once the logs were simplified, we calculated the determinant for each matrix separately, as shown in the step by step solution. Determinants are also multiplicative, which means the determinant of the product of two matrices is the product of their determinants, and that's exactly what was needed to solve the original exercise. Learning and understanding the process of matrix determinant calculation is incredibly beneficial for higher-level mathematics, including linear algebra and differential equations.
In our exercise, once the logs were simplified, we calculated the determinant for each matrix separately, as shown in the step by step solution. Determinants are also multiplicative, which means the determinant of the product of two matrices is the product of their determinants, and that's exactly what was needed to solve the original exercise. Learning and understanding the process of matrix determinant calculation is incredibly beneficial for higher-level mathematics, including linear algebra and differential equations.