Sigma Percentile
JEE Main 2022 (29 June Shift 2)
LEVELJEE Main

Animated Solution for Mathematics - Complex Numbers: Let be a root of the equation . Then the value of is equal to:

Select Answer:

Visualized Solution

The Given Equation

  • Given equation:
  • The variable is a root of this equation.
  • We need to evaluate:

Factorization Strategy

  • To factorize , we can complete the square.
  • Add and subtract :
  • This forms a perfect square:

Splitting into Quadratics

  • Use the difference of squares identity:
  • Apply to our equation:
  • Rearranging gives two quadratic equations:
  • or

Identifying the Roots

  • Case 1:
  • The roots are the complex cube roots of unity:
  • Case 2:
  • The roots are:

Visualizing the Roots on the Complex Plane

  • The roots lie on the unit circle in the complex plane.
  • and are at angles and .
  • and are at angles and .

The Power Property

  • If is a root of , then .
  • If is a root of , then .
  • We will use these properties to simplify the large powers.

Analyzing the Target Expression

  • Target:
  • Notice that all exponents are multiples of :
  • (Odd multiple)
  • (Even multiple)
  • (Odd multiple)

Rewriting the Expression

  • Rewrite using the power of a power rule:
  • Expression becomes:
  • Now we can evaluate this for both possible values of .

Case 1:

  • Substitute into the expression:
  • Since raised to any power is :

Case 2:

  • Substitute into the expression:
  • Recall: and

Final Result and Summary

  • In both cases, the value of the expression is .
  • The result is independent of which specific root represents.
  • Final Answer: 1

The Sigma Insight: Cube Roots and nth Roots of Unity

Solution Diagram

Analyzing the Setup

Imagine you are standing before a massive, intimidating algebraic expression: . It looks like a mountain, but in the world of JEE Advanced, every mountain has a path to the summit.
Our journey begins with the equation . To reveal its secret, we use the technique of completing the square by adding and subtracting :
Suddenly, the expression transforms into . This is the key that unlocks the door.

The Dance of the Roots

With the difference of squares identity, , we can split our equation into two elegant quadratic factors:
This gives us two distinct paths: and .
If is a root of the first, it is a complex cube root of unity, meaning . If is a root of the second, it is a cube root of , meaning . This is the fundamental realization that simplifies our massive exponents.

The Power of Three

Now, look at our target expression: . Notice that all the exponents are multiples of .
We can rewrite them as:
This is where the magic happens. Whether or , the expression collapses into a simple arithmetic problem.
If , we get:
If , we get:
In both cases, the result is the same. The complexity vanishes, leaving us with the elegant final answer of 1.

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