JEE Main20199 Apr 2019Morning ShiftMathematicsDeterminantsActual
Let α and β be the roots of the equation x 2 + x + 1 = 0 . Then for y ≠ 0 in R , y + 1 α β α y + β 1 β 1 y + α is equal to
Options
- Ay 3
- By ( y 2 – 1 )
- Cy 3 – 1
- Dy ( y 2 – 3 )
Correct answer
A. y 3
Step-by-step solution
Roots of the equation x 2 + x + 1 = 0 are α and β and we know that the sum of roots of a quadratic equation a x 2 + b x + c = 0 is - b a and c a respectively. ⇒ α + β = - 1 and α β = 1 . Now, let ∆ = y + 1 α β α y + β 1 β 1 y + α Applying R 1 → R 1 + R 2 + R 3 , we get ∆ = y + 1 + α + β y + 1 + α + β y + 1 + α + β α y + β 1 β 1 y + α = y + 1 + α + β 1 1 1 α y + β