Multiple choice

What is the 50th term of the sequence -1, 8, 23, 44,...?

  1. 7796

  2. 7696

  3. 7596

  4. 7496
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sequence: -1, 8, 23, 44. Differences: 9, 15, 21. Second differences: 6, 6. This is a quadratic sequence: an^2 + bn + c. 2a = 6 => a = 3. 3a + b = 9 => 9 + b = 9 => b = 0. a + b + c = -1 => 3 + 0 + c = -1 => c = -4. Term = 3n^2 - 4. 50th term = 3 * 2500 - 4 = 7500 - 4 = 7496.

Keep practicing — related questions