Math Problem Statement
Find the minimum value of : \frac{{{{\log }a}\left( {bc} \right) + {{\log }b}\left( {ac} \right) + {{\log }c}\left( {ab} \right)}}{{{{\log }{ab}}c + {{\log }{bc}}a + {{\log }{ca}}b}} where a, b, c ∈ (0, 1) ∪ (1, ∞).
Solution
We need to find the minimum value of the expression:
Step 1: Simplify the Numerator
We start by simplifying the numerator term by term using the logarithmic identity:
So:
Therefore, the numerator becomes:
Step 2: Simplify the Denominator
We now simplify the denominator using the logarithmic identity:
So:
Therefore, the denominator becomes:
Step 3: Consider Symmetry and Apply the AM-GM Inequality
Let’s assume . In this case, the numerator simplifies to:
This approach seems unsuitable, so we look at another symmetrical scenario. Consider using the AM-GM inequality in the denominator.
The expression for the denominator can be handled by the inequality:
Given that this is a cyclic sum, the minimum possible value of this expression considering AM-GM is 1.
If , the minimum value is achieved and equals to 2.
So, if , we conclude that both the numerator and the denominator simplify to the same form, leading to a minimum value of:
Thus, the minimum value of the expression is 2.
Would you like to explore the specific steps or assumptions made in this solution? Or perhaps a different problem?
Here are five questions related to this topic:
- How does the AM-GM inequality apply to logarithmic functions?
- What happens if , , and are distinct but close in value?
- Can the minimum value of the expression change if , , and belong to different ranges?
- What are the implications of different logarithmic bases for such an expression?
- How would you handle the expression if logarithms with different bases were not allowed?
Tip: Always check for symmetry when solving expressions with multiple variables—it can often simplify the problem significantly.
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Math Problem Analysis
Mathematical Concepts
Logarithms
AM-GM Inequality
Formulas
Logarithmic identities
AM-GM inequality
Theorems
Arithmetic Mean-Geometric Mean Inequality (AM-GM Inequality)
Suitable Grade Level
Advanced High School / College
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