Question

If $15<x<30,$ then $f\left(x\right)=|x-15|+|x-30|$ is

• A. Increasing
• B. Decreasing
• C. Constant
• D. Cannot be determined

Answer 1

The correct option is C Constant

$f\left(x\right)=\{\begin{array}{cc}-2x+45,& x\le 15\\ 15,& 15<x<30\\ 2x-45,& x\ge 30\end{array}$


$\forall x_1,x_2\in (15,30);$
$f\left(x_1\right)=f\left(x_2\right)$