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Find the sum of all solutions of $4^{x} - 3 \cdot 2^{x + 1} + 8 = 0$ .

Competition practiceAlgebra

A3
B6
C2
D8

Step-by-Step Solution

Put

t = 2^{x} : t^{2} - 6 t + 8 = 0

, so

t = 2

or 4, giving

x = 1

or 2. Their sum is 3. (6 is the sum of the t-values.)

Answer: A) 3

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