JAMB Mathematics 2021 Objective — Question 6

Question 6 of 40 from the Joint Admissions and Matriculation Board (JAMB) Mathematics 2021 Objective paper, with the correct answer and a full explanation.

6. log₂x + 2logₓ 2 = 3, x can be (a) 2 or 3 (b) 2 or 4 (c) 1 or 4 (d) 0 or 1

A. 2 or 3
B. 2 or 4Correct
C. 1 or 4
D. 0 or 1

Explanation

Let log₂x = a, so logₓ 2 = 1/a. Then a + 2/a = 3, giving a² - 3a + 2 = 0, so a = 1 or 2. If a=2, x=2²=4; if a=1, x=2¹=2. So x = 2 or 4.

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