If a, b, c, d are four positive real numbers such that abcd = 1, then minimum value of (1+ a) (1 + b) (1 + c) (1 + d) is
Answer & explanation
Correct answer: option 3
Applying AM ≥ GM
$\frac{1+a}{2} \geq(a)^{1 / 2}, \frac{1+b}{2} \geq(b)^{1 / 2}, \frac{1+c}{2} \geq(c)^{1 / 2}, \frac{1+d}{2} \geq(d)^{1 / 2}$
Multiplying all focus (1 + a) (1 + b)(1 + c)(1 + d) ≥ 16