Question:medium

The area of the region \[\left\{ (x, y) : y^2 \leq 4x, \, x<4, \, \frac{xy(x - 1)(x - 2)}{(x - 3)(x - 4)}>0, \, x \neq 3 \right\}\]is

Updated On: Jan 13, 2026
  • \( \frac{16}{3} \)
  • \( \frac{64}{3} \)
  • \( \frac{8}{3} \)
  • \( \frac{32}{3} \)
Show Solution

The Correct Option is D

Solution and Explanation

To determine the area of the region defined by the given inequalities and expression, we proceed step-by-step.

  1. Region Definition:
    • The inequality \(y^2 \leq 4x\) defines the region below the parabola \(y^2 = 4x\), which opens to the right with its vertex at the origin.
    • The condition \(x<4\) restricts the region to the left of the vertical line \(x = 4\).
    • The expression \(\frac{xy(x - 1)(x - 2)}{(x - 3)(x - 4)}>0\) requires that the numerator and denominator are either both positive or both negative.
  2. Identifying Valid x-intervals:
    • The critical points for the numerator are \(x = 0, 1, 2\).
    • The critical points for the denominator are \(x = 3, 4\).
    • Since \(x eq 3\) to avoid division by zero, the x-axis is divided into the intervals: \((-\infty, 0), (0, 1), (1, 2), (2, 3), (3, 4)\).
  3. Evaluating Expression Sign:
    • The sign of the expression is evaluated in each interval:
    • Interval \((0, 1):\): The expression is positive.
    • Interval \((1, 2):\): The expression is positive.
    • Interval \((2, 3):\): The expression is positive.
    • Interval \((3, 4):\): The expression is negative.
  4. Area Calculation:
    • The valid x-intervals where the inequality holds are \((0, 1), (1, 2), (2, 3)\).
    • The inequality \(y^2 \leq 4x\) implies \(-\sqrt{4x} \leq y \leq \sqrt{4x}\). For a given x, the length of the vertical segment is \(2\sqrt{4x}\).
    • The area is calculated by integrating this length over the valid x-intervals. Considering the intervals \((0,1), (1,2), (2,3)\), the integration is from \(x=0\) to \(x=3\).
    • The integral of \(2\sqrt{4x}\) from \(x=0\) to \(x=3\) is calculated as follows:
    • The computed area from \(x=0\) to \(x=3\) is:
    • The total area is obtained by doubling this result due to symmetry across the x-axis (or by summing the areas from the individual positive intervals).
    • Therefore, the total area is \(\frac{32}{3}\).

The final answer is \(\frac{32}{3}\).

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