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Need solution for rd sharma maths class 12 chapter 16 Increasing and Decreasing functions exercise Multiple choice question, question 27

Answers (1)

Correct option (b)            

Hint: Iff(x)  is increasing function{f}'(x)>0

Given:f(x)=x^{2}-k x+5

Explanation:It is given that

f(x)=x^{2}-k x+5 …..(i)

Differentiate (i) w.r.t  x


\because f(x) is increasing,{f}'(x)>0

\begin{aligned} &\Rightarrow 2 x-k>0 \\ &\Rightarrow 2 x>k \\ &\because x \in[2,4] \end{aligned} 

So, Maximum value of k is 4

k \in(-\infty, 4) 

Thus if the function is increasing then k \in(-\infty, 4)

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