Sigma Percentile
JEE Advanced 2002
LEVELJEE Main

Animated Solution for Mathematics - Quadratic Equations: The set of all real numbers for which , is

Select Answer:

Visualized Solution

The Modulus Critical Point

  • The inequality is .
  • The modulus term changes its sign at .
  • We must split the real number line into two distinct regions.

Defining the Two Cases

  • Case 1: (Right side of the critical point).
  • Case 2: (Left side of the critical point).

Case 1 Setup ()

  • For , the expression inside the modulus is non-negative.
  • Therefore, .
  • Substitute into the inequality: .

Simplifying Case 1

  • Expand the bracket: .
  • The terms cancel out.
  • Simplified inequality: .

Solving

  • The equation has roots at and .
  • The parabola opens upwards, so it is positive outside the roots.
  • Solution for the quadratic: or .

Validating Case 1 Solution

  • We must intersect with our initial condition .
  • Valid interval for Case 1: .

Case 2 Setup ()

  • For , the expression inside the modulus is negative.
  • Therefore, .
  • Substitute into the inequality: .

Simplifying Case 2

  • The double negative becomes positive: .
  • Combine like terms: .

Analyzing

  • Let's check the discriminant .
  • .
  • Since and , the quadratic is always positive.

Validating Case 2 Solution

  • The inequality holds for all real numbers.
  • But we must intersect with our Case 2 condition: .
  • Valid interval for Case 2: .

Combining the Intervals

  • We unite the solutions from both cases.
  • Case 2 gives .
  • Case 1 gives .
  • The point perfectly bridges the first two intervals.

Final Solution Set

  • The combined continuous interval is .
  • The right interval remains .
  • Final Answer: .

The Sigma Insight: Solution of Quadratic Equations

Solution Diagram

Analyzing the Setup

The inequality contains an absolute value term that changes behavior at the critical point . To solve this, we must partition the number line into two distinct regions based on the sign of the expression inside the modulus.

Phase 1

The Right Side ()
In the region where , the expression is non-negative. By the definition of the modulus, .
Substituting this into the inequality, we obtain:
Simplifying the expression:
The roots of are . Since the parabola opens upwards, the inequality holds for or .
Applying the boundary condition , we find the intersection:

Phase 2

The Left Side ()
Now, we consider the region where . Here, is negative, so the modulus negates the expression: .
Substituting this into the original inequality:
To analyze this quadratic, we calculate the discriminant :
Since and the leading coefficient is positive, the quadratic is always positive for all real . Given our condition , the solution for this case is:

Phase 3

The Grand Synthesis
We now combine the solutions from both cases using the union operator. From Case 1, we have , and from Case 2, we have .
The point acts as a bridge, connecting and $

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