Solve for $x$: $4^x = 8^{x-1}$
A3CORRECT
B2
C4
D$\frac{3}{2}$
GCEMathematicsIndices, Logarithms and Surds2020
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Why the answer is A, and why the others tempt you.
Express both sides as powers of 2: $2^{2x} = 2^{3(x-1)}$, so $2x = 3x - 3$, giving $x = 3$. A common error is equating $2x = 3x + 3$ from a sign mistake, yielding $x = -3$ or other wrong values.
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