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JEE Main 20266 AprilEvening Shift
Exam
JEE Main
Year
2026
Date
6 April
Shift
Evening Shift
Subject
Mathematics
Chapter
Continuity and Differentiability

JEE Main 2026 · 6 April · Evening Shift · Mathematics · Continuity and Differentiability

Let f(x) = cases x^3 + 8 ; & x Then the number of points, where the...

Let f(x)=f(x) =\begin{cases} x^3 + 8 ; & x < 0 \\ x^2 - 4 ; & x \geq 0 \end{cases}and $g(x) = $\begin{cases} (x-8)^{1/3} ; & x < 0 \\ (x+4)^{1/2} ; & x \geq 0 \end{cases}.
Then the number of points, where the function g∘fg \circ f is discontinuous, is __________.

Correct answer

0

Step-by-step solution

The possible points of discontinuity for the composite function g(f(x))g(f(x)) are the points where f(x)f(x) is discontinuous and the points where f(x)f(x) is equal to a point of discontinuity of g(x)g(x).

First, we find the points of discontinuity of f(x)f(x) and g(x)g(x).

For f(x)f(x), the only possible point of discontinuity is at x=0x = 0.
lim⁡x→0−f(x)=lim⁡x→0−(x3+8)=8\lim_{x \to 0^-} f(x) = \lim_{x \to 0^-} (x^3 + 8) = 8
lim⁡x→0+f(x)=lim⁡x→0+(x2−4)=−4\lim_{x \to 0^+} f(x) = \lim_{x \to 0^+} (x^2 - 4) = -4
Since lim⁡x→0−f(x)≠lim⁡x→0+f(x)\lim_{x \to 0^-} f(x) \neq \lim_{x \to 0^+} f(x), f(x)f(x) is discontinuous at x=0x = 0.

For g(x)g(x), the only possible point of discontinuity is at x=0x = 0.
lim⁡x→0−g(x)=lim⁡x→0−(x−8)1/3=−2\lim_{x \to 0^-} g(x) = \lim_{x \to 0^-} (x - 8)^{1/3} = -2
lim⁡x→0+g(x)=lim⁡x→0+(x+4)1/2=2\lim_{x \to 0^+} g(x) = \lim_{x \to 0^+} (x + 4)^{1/2} = 2
Since lim⁡x→0−g(x)≠lim⁡x→0+g(x)\lim_{x \to 0^-} g(x) \neq \lim_{x \to 0^+} g(x), g(x)g(x) is discontinuous at x=0x = 0.

Next, we find the points where f(x)f(x) equals the point of discontinuity of g(x)g(x), which is f(x)=0f(x) = 0.
For x<0x < 0, x3+8=0⇒x=−2x^3 + 8 = 0 \Rightarrow x = -2.
For x≥0x \geq 0, x2−4=0⇒x=2x^2 - 4 = 0 \Rightarrow x = 2.

Thus, the possible points of discontinuity for g(f(x))g(f(x)) are x=−2x = -2, x=0x = 0, and x=2x = 2. We check the continuity at each of these points.

At x=−2x = -2:
As x→−2−x \to -2^-, f(x)→0−f(x) \to 0^-, so lim⁡x→−2−g(f(x))=lim⁡y→0−g(y)=−2\lim_{x \to -2^-} g(f(x)) = \lim_{y \to 0^-} g(y) = -2
As x→−2+x \to -2^+, f(x)→0+f(x) \to 0^+, so lim⁡x→−2+g(f(x))=lim⁡y→0+g(y)=2\lim_{x \to -2^+} g(f(x)) = \lim_{y \to 0^+} g(y) = 2
Since the left-hand limit and right-hand limit are not equal, g(f(x))g(f(x)) is discontinuous at x=−2x = -2.

At x=0x = 0:
lim⁡x→0−g(f(x))=g(8)=(8+4)1/2=23\lim_{x \to 0^-} g(f(x)) = g(8) = (8 + 4)^{1/2} = 2\sqrt{3}
lim⁡x→0+g(f(x))=g(−4)=(−4−8)1/3=(−12)1/3\lim_{x \to 0^+} g(f(x)) = g(-4) = (-4 - 8)^{1/3} = (-12)^{1/3}
Since the limits are not equal, g(f(x))g(f(x)) is discontinuous at x=0x = 0.

At x=2x = 2:
As x→2−x \to 2^-, f(x)→0−f(x) \to 0^-, so lim⁡x→2−g(f(x))=lim⁡y→0−g(y)=−2\lim_{x \to 2^-} g(f(x)) = \lim_{y \to 0^-} g(y) = -2
As x→2+x \to 2^+, f(x)→0+f(x) \to 0^+, so lim⁡x→2+g(f(x))=lim⁡y→0+g(y)=2\lim_{x \to 2^+} g(f(x)) = \lim_{y \to 0^+} g(y) = 2
Since the limits are not equal, g(f(x))g(f(x)) is discontinuous at x=2x = 2.

Therefore, there are 33 points of discontinuity.

Answer: 33
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