MCQMediumJEE 2023Continuity

JEE Mathematics 2023 Question with Solution

Let ff, gg and hh be the real valued functions defined on R\mathbb{R} as f(x)={xx,x0f(x) = \left\lbrace \begin{array}{ll} \frac{x}{|x|}, & x \neq 0\end{array} \right.

  • A

    ff is continuous at x=0x = 0

  • B

    gg is continuous at x=0x = 0

  • C

    hh is continuous at x=0x = 0

  • D

    f,g,hf, g, h are continuous at x=0x = 0

Answer

Correct answer:A

Step-by-step solution

Standard Method

Given: the solution concludes that the correct option is A.

Find: Which statement about continuity at x=0x = 0 is correct.

From the extracted working, the left-hand limit and right-hand limit being checked are:

LHL=limk0,  k>0g(h(k))\text{LHL} = \lim_{k \to 0,\; k>0} g(h(-k))

and

RHL=limk0,  k>0g(h(k))\text{RHL} = \lim_{k \to 0,\; k>0} g(h(k))

Using the shown fact,

f(x)=1x<0f(x) = -1 \quad \forall x < 0

so the left-side evaluation gives

g(1)=1g(-1) = 1

Also, using the shown fact,

f(x)=1x>0f(x) = 1 \quad \forall x > 0

so the right-side evaluation also gives

g(1)=1g(-1) = 1

and hence the limit value obtained from both sides is the same.

Therefore, as per the provided the solution, the correct option is A.

Common mistakes

  • Using the incomplete question statement as if all definitions of gg and hh were available. This is wrong because the given question is truncated. Use the solution as the authority for the final answer extraction.

  • Assuming f(x)=xxf(x)=\frac{x}{|x|} is continuous at x=0x=0 directly. This is wrong because ff is not even defined at x=0x=0 in the displayed definition. Do not infer continuity without the full original question context.

  • Confusing one-sided values of the sign-type function near 00. For x<0x<0, xx=1\frac{x}{|x|}=-1 and for x>0x>0, xx=1\frac{x}{|x|}=1. Keep left-hand and right-hand behavior separate.

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