2018 · Q20
The sum of a number and its square is 20. Then the number is
Elementary MathematicsAlgebra
- A-5 or 4
- B2 or 3
- C-5 only
- D5 or -4
Explanation
n + n² = 20 gives n² + n − 20 = 0, which factors as (n + 5)(n − 4) = 0. Hence n = −5 or n = 4, option (A). Option (C) wrongly discards the negative root.