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Let f (x) = x ^(3//2) - sqrt ( x ^(2) + ...

Let `f (x) = x ^(3//2) - sqrt ( x ^(2) + x ^(4)),` then

A

L.H.D. at `x =0` exists but R.D.H. at `x =0` does not exist

B

f (x) is differentiable at x =0

C

R.H.D. at `x =0` exists but L.H.D. at `x =0` does not exists

D

None of these

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the function \( f(x) = x^{3/2} - \sqrt{x^2 + x^4} \) and determine the existence of the left-hand and right-hand derivatives at \( x = 0 \). ### Step 1: Calculate \( f(0) \) First, we need to find the value of the function at \( x = 0 \): \[ f(0) = 0^{3/2} - \sqrt{0^2 + 0^4} = 0 - 0 = 0 \] ### Step 2: Find the Right-Hand Derivative at \( x = 0 \) The right-hand derivative at \( x = 0 \) is given by: \[ f'_+(0) = \lim_{h \to 0^+} \frac{f(h) - f(0)}{h} \] Substituting \( f(0) = 0 \): \[ f'_+(0) = \lim_{h \to 0^+} \frac{f(h)}{h} \] Now, substituting \( f(h) \): \[ f(h) = h^{3/2} - \sqrt{h^2 + h^4} \] Thus, \[ f'_+(0) = \lim_{h \to 0^+} \frac{h^{3/2} - \sqrt{h^2 + h^4}}{h} \] ### Step 3: Simplify the Expression We can simplify the expression: \[ f'_+(0) = \lim_{h \to 0^+} \left( h^{1/2} - \frac{\sqrt{h^2(1 + h^2)}}{h} \right) \] This simplifies to: \[ f'_+(0) = \lim_{h \to 0^+} \left( h^{1/2} - \sqrt{1 + h^2} \right) \] ### Step 4: Evaluate the Limit As \( h \to 0 \): \[ h^{1/2} \to 0 \quad \text{and} \quad \sqrt{1 + h^2} \to 1 \] Thus, \[ f'_+(0) = 0 - 1 = -1 \] ### Step 5: Find the Left-Hand Derivative at \( x = 0 \) The left-hand derivative at \( x = 0 \) is given by: \[ f'_-(0) = \lim_{h \to 0^-} \frac{f(h) - f(0)}{h} \] Substituting \( f(0) = 0 \): \[ f'_-(0) = \lim_{h \to 0^-} \frac{f(h)}{h} \] Now, substituting \( f(h) \): \[ f(h) = (-h)^{3/2} - \sqrt{(-h)^2 + (-h)^4} \] Since \( (-h)^{3/2} \) is not defined for negative \( h \) (as it results in a complex number), we cannot compute this limit. ### Step 6: Conclusion Since the left-hand derivative does not exist and the right-hand derivative exists, we conclude: - The right-hand derivative at \( x = 0 \) exists and is equal to \(-1\). - The left-hand derivative at \( x = 0 \) does not exist. Thus, the correct option is that the right-hand derivative at \( x = 0 \) exists, but the left-hand derivative does not.
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