Daily Problem, November 10, 2026: Quadratic equations

By the FreeMathSchool team ·

The problem

Solve: x2 − 9x + 8 = 0

Answer

x = 1, or x = 8

Worked solution

  1. Find two numbers that multiply to 8 and add to −9: −1 and −8.
  2. Factor: (x − 1)(x − 8) = 0
  3. Set each factor to zero: x = 1 or x = 8.
  4. Check with the quadratic formula: b² − 4ac = 49, so x = (9 ± 7) ÷ 2, which gives 8 and 1.

How members answered

  • 17tried
  • 65%first try
  • 12solved

Common mistakes

  • Those are the numbers inside the factors. The roots have the opposite sign: x − 1 = 0 gives x = 1. (2 people)

Top wrong answers: −1, −8 (2).