Multiple choice

Find the 20th term of the given sequence. 4, 6, 10, 16,...

  1. 342

  2. 364

  3. 372

  4. 384
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sequence: 4, 6, 10, 16. Differences: 2, 4, 6. This is a quadratic sequence. a_n = an^2 + bn + c. a_1 = a+b+c=4, a_2 = 4a+2b+c=6, a_3 = 9a+3b+c=10. Subtracting: 3a+b=2, 5a+b=4. 2a=2, a=1. b=-1. c=4. a_n = n^2 - n + 4. a_20 = 400 - 20 + 4 = 384.

Keep practicing — related questions