NDA 2025
- Exam
- NDA
- Year
- 2025
- Subject
- Mathematics
- Chapter
- Quadratic Equation
NDA 2025 · Mathematics · Quadratic Equation
If x^2 - x + 1 = 0 , then what is (x - (1)/(x))^2 + (x - (1)/(x))^4...
If , then what is \left(x - \dfrac{1}{x}\right)^2 + equal to?
Options
- A
- B
- C
- D
Correct answer
C.
Step-by-step solution
Given
Dividing the entire equation by , we get:
Using the algebraic identity \left(x - \dfrac{1}{x}\right)^2 = \left(x + \dfrac{1}{x}\right)^2 - 4x + \dfrac{1}{x}
The given expression is \left(x - \dfrac{1}{x}\right)^2 + \left(x - \dfrac{1}{x}\right)^4 + \left(x - \dfrac{1}{x}\right)^8
Substituting \left(x - \dfrac{1}{x}\right)^2 = -3(-3) + (-3)^2 + (-3)^4= -3 + 9 + 81= 8787
Dividing the entire equation by , we get:
Using the algebraic identity \left(x - \dfrac{1}{x}\right)^2 = \left(x + \dfrac{1}{x}\right)^2 - 4x + \dfrac{1}{x}
The given expression is \left(x - \dfrac{1}{x}\right)^2 + \left(x - \dfrac{1}{x}\right)^4 + \left(x - \dfrac{1}{x}\right)^8
Substituting \left(x - \dfrac{1}{x}\right)^2 = -3(-3) + (-3)^2 + (-3)^4= -3 + 9 + 81= 8787