passwella.
Menu

OAU Post-UTME Mathematics 2022 (Batch A) Question 7

Question 7

Quadratic Equations

The roots of the equation 2x2 + kx + 5 = 0 are α and β, where k is a constant. If α2 + β2 = −1, find the values of k

  1. A.±4
  2. B.±2
  3. C.±1
  4. D.±3
Show the answer and explanation

Answer: A (±4)

Explanation

α + β = −k/2 and αβ = 5/2. α² + β² = (α + β)² − 2αβ = k²/4 − 5 = −1, so k² = 16 and k = ±4.