Question

If log₂ (a + b) + log₂ (c + d) ³ 4. Then the min. value of the expression a + b + c + d is –

• A. 2
• B. 4
• C. 8
• D. None of these

Answer 1

Answer: (C)

8

Answer 2

log₂ (a + b) + log₂ (c + d) ³ 4

log₂ [(a + b) (c + d)} ³ 4

(a + b) (c + d) ³ 2⁴

$\frac{(a + b) + (c + d)}{2}$ ³ $\sqrt{(a + b)(c + d)}$

$\frac{a + b + c + d}{2}$ ³ 2²

a + b + c + d ³ 8