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Match List-I with List-II

List-IList-II
(A) f(x)=xsin⁡xf(x) = x \sin x(I) is not continuous at x=−3x = -3
(B) f(x)=∣x∣x,x≠0f(x) = \frac{\vert x\vert }{x}, x \neq 0 and f(x)=1 at x=0f(x) = 1 \text{ at } x = 0(II) is continuous everywhere
(C) f(x)=x−[x]f(x) = x - [x], [x][x] denotes greatest integer function(III) is not differentiable at x=1x = 1
(D) f(x)=e∣x−1∣f(x) = e^{\vert x - 1\vert }(IV) is not continuous at x=0x = 0

Choose the correct answer from the options given below:

Solution

✅ Correct Option: 3

f(x)=xsin⁡xf(x) = x \sin x

Both xx and sin⁡x\sin x are continuous and differentiable everywhere. The product of two continuous functions is always continuous.

So xsin⁡xx \sin x is continuous everywhere.

(A) → (II)


f(x)=∣x∣x, x≠0f(x) = \dfrac{|x|}{x},\ x \neq 0 and f(0)=1f(0) = 1

When x>0x > 0: f(x)=xx=1f(x) = \dfrac{x}{x} = 1

When x<0x < 0: f(x)=−xx=−1f(x) = \dfrac{-x}{x} = -1

At x=0x = 0: f(0)=1f(0) = 1

lim⁡x→0−f(x)=−1\lim_{x \to 0^-} f(x) = -1

lim⁡x→0+f(x)=+1\lim_{x \to 0^+} f(x) = +1

Since LHL ≠\neq RHL, the limit does not exist, so ff is not continuous at x=0x = 0.

(B) → (IV)


f(x)=x−[x]f(x) = x - [x] is the fractional part function {x}\{x\}, which is discontinuous at every integer.

At x=−3x = -3:

lim⁡x→−3−f(x)\lim_{x \to -3^-} f(x): here [x]=−4[x] = -4, so f(x)=x+4→−3+4=1f(x) = x + 4 \to -3 + 4 = 1

lim⁡x→−3+f(x)\lim_{x \to -3^+} f(x): here [x]=−3[x] = -3, so f(x)=x+3→−3+3=0f(x) = x + 3 \to -3 + 3 = 0

f(−3)=−3−[−3]=−3+3=0f(-3) = -3 - [-3] = -3 + 3 = 0

Since LHL (=1)≠(= 1) \neq RHL (=0)(= 0), ff is not continuous at x=−3x = -3.

(C) → (I)


The function is given by:

f(x)=e∣x−1∣f(x) = e^{|x-1|}

Since ∣x−1∣|x-1| is continuous everywhere, e∣x−1∣e^{|x-1|} is also continuous everywhere.

However, ∣x−1∣|x-1| has a sharp corner point at x=1x = 1, so differentiability must be checked specifically at that point using first principles.

Left-Hand Derivative (LHD):

lim⁡h→0−f(1+h)−f(1)h=lim⁡h→0−e∣h∣−e0h\lim_{h \to 0^-} \frac{f(1+h) - f(1)}{h} = \lim_{h \to 0^-} \frac{e^{|h|} - e^0}{h}

Since h→0−h \to 0^-, hh is negative, which means ∣h∣=−h|h| = -h:

lim⁡h→0−e−h−1h=−1\lim_{h \to 0^-} \frac{e^{-h} - 1}{h} = -1

Right-Hand Derivative (RHD):

lim⁡h→0+f(1+h)−f(1)h=lim⁡h→0+e∣h∣−e0h\lim_{h \to 0^+} \frac{f(1+h) - f(1)}{h} = \lim_{h \to 0^+} \frac{e^{|h|} - e^0}{h}

Since h→0+h \to 0^+, hh is positive, which means ∣h∣=h|h| = h:

lim⁡h→0+eh−1h=+1\lim_{h \to 0^+} \frac{e^{h} - 1}{h} = +1

Since the Left-Hand Derivative (−1-1) ≠\neq Right-Hand Derivative (+1+1), the function f(x)f(x) is not differentiable at x=1x = 1.

Therefore, (D) →\rightarrow (III)


(A) → (II)

(B) → (IV)

(C) → (I)

(D) → (III)

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