Question

The minimum value of $f\left(x\right)=9x+\frac{25}{x},x>0$ is

• A. 34
• B. -34
• C. 30
• D. -30

Answer 1

Answer: (C)

30

Use A.M. & G.M.
$\frac{9x+\frac{25}{x}}{2}\ge (9x\times \frac{25}{x}{)}^{\frac{1}{2}}$
$9x+\frac{25}{x}\ge 30$