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Need solution for RD Sharma maths class 12 chapter 8 Continuity exercise multiple choice question 27

Answers (1)


 The correct option is (a)


If a function is continuous at x = a, then  

\lim _{x \rightarrow t} f(x)=\lim _{x \rightarrow 0^{+}} f(x)=f(a)

Solution:  the function


is continuous at every point of its domain

Step 1: Understand that according to question, f(x) is continuous at every point of its domain.

Therefore, it is continuous at x = 1

\begin{aligned} &\therefore \lim _{x \rightarrow 1} f(x)=f(1) \\ &\lim _{h \rightarrow 0} f(1+h)=f(1) \\ &\lim _{h \rightarrow 0}\left[4(1+h)^{2}+3 b(1+h)\right]=5(1)-4 \\ &4+3 b=1 \end{aligned}

Simplify further,

\begin{aligned} &3 b=-3 \\ &b=-1 \end{aligned}

Hence, the correct answer is option (a)

Posted by

Gurleen Kaur

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