tentukan nilai k pada deret berikut a. 4+10+16+22....+k=444

Arithmetic Series.

4 + 10 + 16 + 22 + ... + k = 444
Sn = n/2 [2a + (n - 1)b]
444 = n/2 [2(4) + (k - 1)(6)]
444 = n/2 (6n + 2)
3n² + k - 444 = 0
n = 12 or n = -37/3 ← Not solution.

k is 12 th term, so:
Un = a + (n - 1)b
U₁₂ = 4 + (12 - 1)(6)
k = 70