Question

$f\left(x\right)={\log }_{a}x(x>0)$ is decreasing function if

• A. $a>1$
• B. $0<a<1$
• C. $a\ne 1$
• D. $a\ne 0$

Answer 1

Answer: (B)

$0<a<1$

$f\left(x\right)=\frac{logx}{loga}$
$f^{\prime }\left(x\right)=\frac{1}{xloga}$
$f^{\prime }\left(x\right)<0$ If $0<a<1$