Advanced Math practice question

Answer: 2

Let u = 2ˣ: u² − 5u + 4 = 0 → (u − 1)(u − 4) = 0 → 2ˣ = 1 or 2ˣ = 4 → x = 0 or x = 2. The sum is 2.

Common wrong answers

If you answered 3

3 comes from 2ˣ = 4 giving x = 2 and 2ˣ = 1 giving x = 1 (a slip: 2⁰ = 1).

If you answered 4

4 is 1 × 4, the product of the u-values.

If you answered 5

5 is the sum of the u-values (1 + 4), not of the x-values.

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