More Questions from Surds and Indices

$\frac{1}{1 + x^{(b-a)} + x^{(c-a)}} + \frac{1}{1 + x^{(a-b)} + x^{(c-b)}} + \frac{1}{1 + x^{(b-c)} + x^{(a-c)}} =$ $x$

Aptitude Surds and Indices Difficulty: Hard
Choose an option
  • A
    0
  • B
    1
  • C
    $x^{a-b-c}$
  • D
    None of these

Answer

Correct Answer: 1

Explanation

Concept & Logic This question tests your ability to manipulate negative exponents and find a common denominator across cyclic fractions. The fundamental rule of negative exponents states: $$x^{-n} = \frac{1}{x^n}$$ In this expression, we can rewrite terms like $x^{(b-a)}$ as $\frac{x^b}{x^a}$. Multiplying the numerator and denominator of each fraction by the denominator's hidden base will normalize all three fractions to share the exact same common denominator. Step-by-step Solution Let's handle the three main fractional terms one by one. For the first term: $$\frac{1}{1 + \frac{x^b}{x^a} + \frac{x^c}{x^a}}$$ Multiply the numerator and the denominator by $x^a$: $$\frac{x^a}{x^a(1) + x^a(\frac{x^b}{x^a}) + x^a(\frac{x^c}{x^a})} = \frac{x^a}{x^a + x^b + x^c}$$ For the second term: $$\frac{1}{1 + \frac{x^a}{x^b} + \frac{x^c}{x^b}}$$ Multiply the numerator and the denominator by $x^b$: $$\frac{x^b}{x^b + x^a + x^c}$$ For the third term: $$\frac{1}{1 + \frac{x^b}{x^c} + \frac{x^a}{x^c}}$$ Multiply the numerator and the denominator by $x^c$: $$\frac{x^c}{x^c + x^b + x^a}$$ Now, add the three simplified fractions together. Since all three have the exact same denominator $(x^a + x^b + x^c)$, you can simply add their numerators: $$\frac{x^a + x^b + x^c}{x^a + x^b + x^c}$$ Any non-zero expression divided by itself equals $1$. Exam Strategy & Shortcut **Symmetry & Value Putting**: This expression is perfectly symmetrical concerning $a$, $b$, and $c$. For any such generalized cyclic expression where the options are constants (like 0 and 1), assume simple identical values for the variables. Let $a = 1$, $b = 1$, $c = 1$. The expression becomes: $\frac{1}{1 + x^0 + x^0} + \frac{1}{1 + x^0 + x^0} + \frac{1}{1 + x^0 + x^0}$ Since $x^0 = 1$, this turns into $\frac{1}{1+1+1} + \frac{1}{1+1+1} + \frac{1}{1+1+1} = \frac{1}{3} + \frac{1}{3} + \frac{1}{3} = 1$. Common Pitfall Students often waste time trying to find the Least Common Multiple (LCM) of the massive original denominators without simplifying the negative exponents first. This leads to a horrific algebraic mess that consumes too much time. Final Answer **Therefore, the correct answer is 1.**
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