Question:medium

If \[ f(x) = \begin{cases} x^3 - x^2 + 1, & \text{if } x > 0 \\ e^x \sin x + i x + \lambda \log 4, & \text{if } x \leq 0 \end{cases} \]
is continuous at \( x = 0 \), then the value of 500\(\lambda\) is:

Show Hint

When dealing with piecewise functions, ensure the limits from both sides match at the point of continuity. Use the definition of continuity to set the limits equal and solve for unknowns.
Updated On: Jun 30, 2026
  • 1000
  • 2000
  • 4000
  • 3000
Show Solution

The Correct Option is C

Solution and Explanation

Step 1: Understanding the Question:
For a function to be continuous at \( x = 0 \), the left-hand limit (LHL), right-hand limit (RHL), and the functional value at \( x = 0 \) must be equal.
Step 2: Key Formula or Approach:
We evaluate \( \lim_{x \to 0^+} f(x) \) and \( \lim_{x \to 0^-} f(x) \) and equate them.
Step 3: Detailed Explanation:
RHL (\( x \to 0^+ \)):
\[ \lim_{x \to 0^+} \frac{8^x - 4^x - 2^x + 1}{x^2} = \lim_{x \to 0^+} \frac{4^x(2^x - 1) - 1(2^x - 1)}{x^2} \] \[ = \lim_{x \to 0^+} \frac{(4^x - 1)(2^x - 1)}{x^2} = \lim_{x \to 0^+} \left( \frac{4^x - 1}{x} \right) \left( \frac{2^x - 1}{x} \right) \] Using the standard limit \( \lim_{h \to 0} \frac{a^h - 1}{h} = \ln a \):
RHL = \( \ln 4 \cdot \ln 2 \).
LHL (\( x \to 0^- \)):
\[ f(0) = \lim_{x \to 0^-} (\text{e}^x \sin x + ix + \lambda \ln 4) \] Substituting \( x = 0 \):
LHL = \( \text{e}^0 \sin 0 + i(0) + \lambda \ln 4 = \lambda \ln 4 \).
Equating LHL and RHL:
\( \lambda \ln 4 = \ln 4 \cdot \ln 2 \)
\( \lambda = \ln 2 \).
Now, we need the value of \( 500\text{e}^{\lambda} \):
\( \text{e}^{\lambda} = \text{e}^{\ln 2} = 2 \).
Value = \( 500 \times 2 = 1000 \).
Step 4: Final Answer:
The value is 1000.
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