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Question

If \(a^b = b^a\), then what is 

\(\frac{a \times   (\frac{a}{b}) ^{ \frac{a}{b} } }{ (a)^{ \frac{a}{b} } }\) 

equal to?

This question was previously asked in
CDS 2 2025 Maths Question Paper (14-Sep-2025)
The correct answer is
1

Understanding the Problem

We are given an equation relating two variables, \(a^b = b^a\), and asked to find the value of a specific mathematical expression involving these variables:

\(E = \frac{a \times \left(\frac{a}{b}\right)^{ \frac{a}{b} } }{ a^{ \frac{a}{b} } }\)

Our goal is to simplify this expression using the given condition.

Simplifying the Expression

Let's break down the simplification process step-by-step:

  1. Rewrite the expression using the properties of exponents. Specifically, we can rewrite the division as multiplication by a negative exponent: \(E = a \times \left(\frac{a}{b}\right)^{ \frac{a}{b} } \times a^{ - \frac{a}{b} }\)
  2. Group terms with the same base (\(a\) and \(b\)). Recall that \(\left(\frac{a}{b}\right)^{ \frac{a}{b} } = \frac{a^{ \frac{a}{b} }}{b^{ \frac{a}{b} }}\). Substituting this in the original expression gives: \(E = \frac{a \times \frac{a^{ \frac{a}{b} }}{b^{ \frac{a}{b} }} }{ a^{ \frac{a}{b} } }\) Now, simplify the fraction: \(E = a \times \frac{a^{ \frac{a}{b} }}{b^{ \frac{a}{b} }} \times \frac{1}{a^{ \frac{a}{b} }}\)
  3. Cancel out common factors. The term \(a^{ \frac{a}{b} }\) appears in both the numerator and the denominator: \(E = a \times \frac{1}{b^{ \frac{a}{b} }}\) \(E = \frac{a}{ b^{ \frac{a}{b} } }\)

Using the Condition \(a^b = b^a\)

Now we need to use the given condition \(a^b = b^a\) to simplify the expression \(E = \frac{a}{ b^{ \frac{a}{b} } }\).

Let's manipulate the condition:

  • Start with \(a^b = b^a\).
  • Raise both sides to the power of \(\frac{1}{b}\): \((a^b)^{\frac{1}{b}} = (b^a)^{\frac{1}{b}}\)
  • Using the exponent rule \((x^m)^n = x^{mn}\), we get: \(a^{b \times \frac{1}{b}} = b^{a \times \frac{1}{b}}\) \(a^1 = b^{\frac{a}{b}}\) \(a = b^{\frac{a}{b}}\)

This gives us a relationship between \(a\) and \(b^{\frac{a}{b}}\).

Final Calculation

Substitute the result \(a = b^{\frac{a}{b}}\) back into our simplified expression for \(E\):

\(E = \frac{a}{ b^{ \frac{a}{b} } }\) \(E = \frac{a}{a}\) \(E = 1\)

Therefore, the value of the given expression is 1.

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Important Questions from Logarithms

  1. Given that $132^{0.14} = x$, $132^{0.26} = y$ and $x^z = y^2$, then the value of z is close to:

  2. For \(x \ge y > 1\), let \(\log_x\left(\frac{x}{y}\right) + \log_y\left(\frac{y}{x}\right) = k\), then the value of \(k\) can never be equal to

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  4. What is the number of solutions of \(\log_4(x-1) = \log_2(x - 3)\)?
  5. Let \(p = \ln(x)\), \(q = \ln(x^3)\) and \(r = \ln(x^5)\), where \(x > 1\). Which of the following statements is/are correct?
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    Select the answer using the code given below.
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