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Need solution for RD Sharma Maths Class 12 Chapter 18 Continuity Excercise 8.1 Question 36 Subquestion (v)

Answers (1)

Answer:

                k=\frac{9}{5}

Hint:

For a function to be continuous at a point, its LHL RHL and value at that point should be equal.

Given:

                f(x)=\left(\begin{array}{l} k x+1, \text { if } x \leq 5 \\\\ 3 x-5, \text { if } x>5 \end{array}\right)

Solution:

                f(x)=\left(\begin{array}{l} k x+1, \text { if } x \leq 5 \\\\ 3 x-5, \text { if } x>5 \end{array}\right)

We have

(LHL at x=5 )

                \lim _{x \rightarrow 5^{-}} f(x)=\lim _{h \rightarrow 0} f(5-h)=\lim _{h \rightarrow 0} k(5-h)+1=5 k+1

(RHL at x=5 )

                \lim _{x \rightarrow 5^{+}} f(x)=\lim _{h \rightarrow 0} f(5+h)=\lim _{h \rightarrow 0} 3(5+h)-5=10

If f\left ( x \right )  is continuous at x=5 , then

                \begin{aligned} &\lim _{x \rightarrow 5^{+}} f(x)=\lim _{x \rightarrow 5^{-}} f(x) \\ &5 k+1=10 \\ &k=\frac{9}{5} \end{aligned}

               

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