Sigma Percentile
JEE Main 2018 (Paper 1)
LEVELJEE Main

Animated Solution for Mathematics - Complex Numbers: If are the distinct roots, of the equation , then is equal to :

Select Answer:

Visualized Solution

The Given Equation

  • Given equation:
  • Roots are and
  • We need to find:

Finding the Roots using Quadratic Formula

  • Using quadratic formula:
  • Substitute :

Identifying Roots as and

  • Recall cube roots of unity: and
  • Our roots are:

Assigning and

  • Let
  • Let
  • Properties of : and

Evaluating

  • Substitute and :

Simplifying

  • Since is odd,
  • So,

Reducing to

  • Divide by :
  • Therefore,

Simplifying

  • Since is odd,

Reducing to

  • Divide by :
  • Therefore,

Substituting back into the Expression

Applying the Identity

  • Using identity:
  • Rearranging gives:

Final Result

  • Substitute back:
  • Final Answer: 1

The Sigma Insight: Cube Roots and nth Roots of Unity

Solution Diagram

Analyzing the Quadratic Foundation

We begin with the given quadratic equation:
Using the quadratic formula , we substitute , , and . This yields:
These values represent our roots, and . They are not merely random complex numbers; they are intrinsically linked to the cube roots of unity.

The Bridge to Unity

Recall the definition of the complex cube roots of unity, where and . If you examine our roots closely, you will notice they are exactly and .
This identification is the critical "Aha!" moment. By recognizing our roots as and , we unlock the two fundamental properties of :

The Power Reduction

Now, we address the expression . Substituting our identified values, we obtain:
Because and are odd, the negative signs persist, resulting in:
We now apply the property by dividing the exponents by . For the first term, , so . For the second term, , so .

The Elegant Conclusion

Our expression simplifies to:
Recalling our second property, , we know that . Substituting this into our expression, we get:
The massive powers have vanished, leaving behind a simple, beautiful integer. The final result is 1.

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