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JEE Main 2025 April
LEVELJEE Main

Animated Solution for Mathematics - Quadratic Equations: The sum of the squares of the roots of and the squares of the roots of , is

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Visualized Solution

The Two Equations

  • We need to find the sum of the squares of the roots for two separate equations.
  • Equation 1:
  • Equation 2:

Substitution in Equation 1

  • Equation 1:
  • Let
  • Since it is an absolute value,

Solving for

  • Substitute :
  • Factorize:
  • Roots for : or
  • Reject because

Roots of Equation 1

  • We have
  • This gives two cases:
  • Roots of Equation 1 are

Sum of Squares for Equation 1

  • Roots are and
  • Sum of squares =

Analyzing Equation 2

  • Equation 2:
  • The critical point for the modulus is
  • We must split the problem into two cases:
  • Case 1:
  • Case 2:

Solving Case 1:

  • For ,
  • Equation becomes:

Checking the Root for Case 1

  • Root:
  • Constraint Check: We assumed
  • Since , this root is rejected.

Solving Case 2:

  • For ,
  • Equation becomes:

Roots of Case 2

  • Quadratic:
  • Let the roots be and .
  • We need .
  • We don't need to find the exact values of and !

Sum of Squares for Equation 2

  • Sum of roots:
  • Product of roots:
  • Identity:
  • Substitute values:

Final Calculation

  • Sum of squares from Equation 1 =
  • Sum of squares from Equation 2 =
  • Total Sum =
  • The final answer is 36.

The Sigma Insight: Solution of Quadratic Equations

Solution Diagram

Analyzing the Setup

Welcome, future engineer. Today, we are not just solving an algebra problem; we are learning the art of mathematical discipline. In the JEE Advanced arena, problems involving absolute values are designed to test your patience and your ability to handle logical branches.
Let us dissect this problem, which asks us to find the sum of the squares of the roots of two distinct equations. Take a deep breath, and let us begin.

The Elegance of Substitution

Look at the first equation: . Many students immediately try to open the modulus by considering cases for . While that works, it is the long, winding road.
Notice the structure: we have a term appearing as a square and as a linear term. This is a classic quadratic pattern in disguise. Let us introduce a substitution: .
Suddenly, the equation transforms into the beautiful, simple quadratic:
Factoring this is trivial: . This gives us or . But here is where the discipline comes in.
We defined . Since an absolute value represents a distance, it must be non-negative (). Thus, we must ruthlessly reject .
We are left with , which implies . This splits into two simple linear equations: and , yielding and . The sum of their squares is . Keep this number safe; we will need it later.

The Critical Point and the Fork in the Road

Now, we turn to the second equation: . Here, substitution fails because of the term. We must confront the modulus directly.
The expression changes its behavior at the critical point . This is our fork in the road. We must analyze two distinct universes:
1. The Universe where : Here, . The equation becomes . Expanding this, we get , which simplifies to:
This is a perfect square: , giving . But wait! We assumed . Since , this root is a ghost—it does not exist in this universe. We reject it.
2. The Universe where : Here, . The equation becomes . This simplifies to:

The Power of Vieta

We have arrived at . We could use the quadratic formula to find the roots, but why do the heavy lifting when we can use the elegance of Vieta's formulas?
Let the roots be and . We know that and . The problem asks for the sum of the squares of the roots, which is .
Using the algebraic identity , we substitute our values:

The Final Tally

We have conquered both parts of this problem. From the first equation, we obtained a sum of squares equal to . From the second equation, we obtained a sum of squares equal to .
Adding these together, we get:
This problem was not just about finding roots; it was about managing constraints, recognizing patterns, and choosing the most efficient path to the solution. You have done well. Keep this logical rigor in your toolkit, and no JEE problem will ever be able to stand against you. The final answer is 36.

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