The equation has two equal real roots. Find .

Answer and explanation

Correct answer: A. 25

  1. Step 1: Equal roots need the discriminant .
  2. Step 2: , so and .
Answer
25.
Why not the others: 10: that is , not . 50: an error doubling the discriminant condition. 5: that is and not its square.

Practise more Number and Algebra.

Free questions with an explanation for every one, and full timed HKDSE (Hong Kong) mock tests.