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Solve for x: 4^x - 3 * 2^(x+3) + 128 = 0.

1. x = 3 or x = 4
2. x = 3 only
3. x = 4 only
4. x = 2 or x = 5

Correct answer: x = 3 or x = 4

Solution

Reduce the exponential equation to a quadratic in t = 2^x, solve it, then convert each root back to x using logarithms base 2.

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