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Which one of the following function is continuous at \mathrm{x=3} ?

Option: 1

\mathrm{f(x)=\left\{\begin{array}{l} 2, \text { if } x=3 \\ x-1, \text { if } x>3 \\ \frac{x+3}{3}, \text { if } x<3 \end{array}\right.}


Option: 2

\mathrm{f(x)=\left\{\begin{array}{l} 4, \text { if }=3 \\ 8-x, \text { if } x \neq 3 \end{array}\right.}-


Option: 3

\mathrm{f(x)=\left\{\begin{array}{l} x+3, \text { if } x \leq 3 \\ x-4, \text { if } x>3 \end{array}\right.}


Option: 4

\mathrm{f(x)=\frac{1}{x^3-27} \text {, if } x \neq 3}


Answers (1)

best_answer

\mathrm{\text { If } L H L=R H L=f(a) \text {, i.e., } \underset{x \rightarrow a^{-}}{\operatorname{Lt}} f(x)=\operatorname{Lt}_{x \rightarrow a^{+}} f(x)=f(a) \text {, }}

then \mathrm{f(x)} is continuous at \mathrm{ x=a}

Let us take option (a)

                         \mathrm{\begin{aligned} & \text { LHL }=\operatorname{Lt}_{x \rightarrow 3^{-}} f(x)=\operatorname{Lt}_{x \rightarrow 3} \frac{x+3}{3}=2 \\ & \text { RHL }=\operatorname{Lt}_{x \rightarrow 3^{+}} f(x)=\operatorname{Lt}_{x \rightarrow 3}(x-1)=2 \end{aligned}}

and \mathrm{f(3)=2} so \mathrm{f(x)} is continuous at \mathrm{x=3}
\mathrm{\therefore} Option (a) is correct

Posted by

Rishi

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