• # question_answer If the function f(x) increases in the interval (a, b) then the function $\phi \,(x)={{[f\,(x)]}^{2}}:$ A) increases in (a, b) B) decreases-in (a, b) C)  we cannot say that$\phi \,(x)$increases or decreases in (a, b) D) none of these

$\phi '\,(x)=2f\,(x).$$f'(x);$ if $f\,(x)>0$ in (a, b) then $\phi '\,(x)>0$ and if $f\,(x)>0$in (a, b) then $\phi '\,(x)>0$$\Rightarrow$ C