COMEDK · Maths · 25. Continuity and Differentiability

\(\begin{aligned}
f(x) &=2 a-x \text { in }-a < x < a \\
&=3 x-2 a \text { in } a \geq x
\end{aligned}\)
Then which of the following is true?

A \(f(x)\) is discontinuous at \(x \simeq a\)
B \(f(x)\) is not differentiable at \(x\)
C \(f(x)\) is differentiable at all \(x \geq a\)
D \(f(x)\) is contimuous at all \(x < a\)

Verified Solution

Answer & Solution

Correct Answer

(D) \(f(x)\) is contimuous at all \(x < a\)

Step-by-step Solution

Detailed explanation

We have, At \(x=a\) \[ \begin{aligned} &\mathrm{LHL}=\lim _{x \rightarrow a}(2 a-x)=2 a-a=a \\ &\mathrm{RHL}=\lim _{x \rightarrow a}(3 x-2 a)=3 a-2 a=a \\ &f(a)=3 a-2 a=a \\ &\because \mathrm{LHL}=\mathrm{RHL}=f(a) . \end{aligned} \] So, \(f(x)\) is continuous at \(x=a\). Now,…

Apply the relevant identity from the chapter and substitute the values established in the previous step, keeping the original constraint in view.

Use the simplified expression to isolate the unknown, then plug the result back into the question setup to confirm the working is internally consistent.

Cross-check against a boundary or limiting case. Both the dimensional balance and the qualitative behaviour at the extreme should agree with the candidate answer.

Combine the steps above to identify the correct option. The remaining choices each fail at least one of the consistency, dimensional, or boundary checks.

Same subject

Explore more questions on app

From COMEDK

Explore more questions on app

\(\begin{aligned}f(x) &=2 a-x \text { in }-a < x < a \\&=3 x-2 a \text { in } a \geq x\end{aligned}\)Then which of the following is true?

Step-by-step Solution

\(\begin{aligned}
f(x) &=2 a-x \text { in }-a < x < a \\
&=3 x-2 a \text { in } a \geq x
\end{aligned}\)
Then which of the following is true?