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Question

If \(4^{x+1} = 64 \times 8^{x}\), find the value of \(x\).

This question was previously asked in
RRB Group D 2024 Question Paper PDF (27-Dec-2025) (Shift 2)
The correct answer is

-4

Express every term with base \(2\): \(4 = 2^2\), \(64 = 2^6\) and \(8 = 2^3\).

So \(4^{x+1} = (2^2)^{x+1} = 2^{2x+2}\) and \(64 \times 8^{x} = 2^{6} \times (2^3)^{x} = 2^{6+3x}\).

Equating the exponents of the equal powers of \(2\): \(2x + 2 = 6 + 3x\).

Solving, \(2 - 6 = 3x - 2x\), so \(x = -4\).

Hence, the value of \(x\) is \(-4\).

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