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GATE DA 2025 Q9: Exponents: 3^(x²) = 27 × 9^x

Question

If a real variable xx satisfies 3x2=27×9x3^{x^2} = 27 \times 9^{x}, then the value of 2x2(2x)2\dfrac{2^{x^2}}{(2^{x})^{2}} is:

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Answer: C (official GATE 2025 final answer key)

Concept used: Equating exponents with a common base.

First step: Write the right side as a power of 3: 27×9x=33+2x27 \times 9^{x} = 3^{3+2x}, so x2=3+2xx^2 = 3 + 2x. The expression asked for is 2x2−2x2^{x^2 - 2x}.

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Source: official GATE 2025 DA question paper and final answer key, organised by IIT Roorkee. Question paper · Answer key