$\left(\frac{x^a}{x^b}\right)^{\frac{1}{ab}} \cdot \left(\frac{x^b}{x^c}\right)^{\frac{1}{bc}} \cdot \left(\frac{x^c}{x^a}\right)^{\frac{1}{ca}} =$ $x$
Aptitude
Surds and Indices
Difficulty: Medium
Choose an option
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A1
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B$\frac{1}{x^{abc}}$
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C$x^{\frac{1}{(ab+bc+ca)}}$
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DNone of these
Answer
Correct Answer: 1
Explanation
Concept & Formula
This problem evaluates your ability to combine the laws of indices with algebraic fraction splitting.
The primary index laws used here are:
$$\frac{x^m}{x^n} = x^{m-n}$$
$$(x^m)^n = x^{mn}$$
The crucial algebraic concept is splitting a fraction with a common denominator into two separate terms:
$$\frac{m - n}{mn} = \frac{m}{mn} - \frac{n}{mn} = \frac{1}{n} - \frac{1}{m}$$
Step-by-step Solution
Let's break down the expression one term at a time.
First, simplify the inner fractions using the division law:
1. First term: $\frac{x^a}{x^b} = x^{a-b}$
2. Second term: $\frac{x^b}{x^c} = x^{b-c}$
3. Third term: $\frac{x^c}{x^a} = x^{c-a}$
Next, apply the outer fractional exponent to each base:
1. First term: $(x^{a-b})^{\frac{1}{ab}} = x^{\frac{a-b}{ab}}$
2. Second term: $(x^{b-c})^{\frac{1}{bc}} = x^{\frac{b-c}{bc}}$
3. Third term: $(x^{c-a})^{\frac{1}{ca}} = x^{\frac{c-a}{ca}}$
Now, use the fraction splitting rule on the exponents:
1. First exponent: $\frac{a-b}{ab} = \frac{a}{ab} - \frac{b}{ab} = \frac{1}{b} - \frac{1}{a}$
2. Second exponent: $\frac{b-c}{bc} = \frac{b}{bc} - \frac{c}{bc} = \frac{1}{c} - \frac{1}{b}$
3. Third exponent: $\frac{c-a}{ca} = \frac{c}{ca} - \frac{a}{ca} = \frac{1}{a} - \frac{1}{c}$
Multiply the terms together by adding their simplified exponents:
$$x^{(\frac{1}{b} - \frac{1}{a}) + (\frac{1}{c} - \frac{1}{b}) + (\frac{1}{a} - \frac{1}{c})}$$
All terms in the exponent cancel out:
$\frac{1}{b} - \frac{1}{b} = 0$
$-\frac{1}{a} + \frac{1}{a} = 0$
$\frac{1}{c} - \frac{1}{c} = 0$
The sum of the exponents is $0$.
$$x^0 = 1$$
Exam Strategy & Shortcut
**Value Putting Technique:** Since this is a generalized cyclic identity, the result will hold true for any non-zero values of $a, b,$ and $c$. Let $a=1, b=1, c=1$.
The expression simplifies to $(\frac{1}{1})^1 \cdot (\frac{1}{1})^1 \cdot (\frac{1}{1})^1 = 1$. This bypasses all the complex fraction arithmetic and secures the answer instantly.
Common Pitfall
Students often get intimidated by the fractional exponents and attempt to find a massive common denominator ($abc$) for the entire expression right at the beginning. This creates unnecessary complexity. Splitting the fractions first is much faster and less error-prone.
Final Answer
**Therefore, the correct answer is 1.**