1.

Let f(x) =`xsqrt(4ax-x^(2)),(agt0)` Then f(x) isA. increasing in (0,3a) decreasing in (3a,4a)B. increasing in (a,4a),decreasing in `(5a,oo)`C. increasing in `(0,4a)`D. none of these

Answer» Correct Answer - 1
f(X)=`xsqrt(4ax-x^(2))`
`therefore f(X) =sqrt(4ax-x^(2))+x(4a-2x)/2sqrt(4ax-x^(2))`
`=(2x(3a-x))/sqrt(4ax-x^(2))`
Now if `f(X)gt0` then
`2x(3a-x)gt0`
`2x(x-3a)lt0`
or x in (0,3a)
Thus f(x) increases in (0,3a) and decreases in (3a,4a)
Thus f(X) increases in (0,3a) and decreases (3a,4a)


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