Question

Помогите решить. Буду крайне благодарен

Answer 1

$Sn = \frac{a1 + an}{2} \times n \\ a1 = 2, a2 = 4, \\ d = a2 - a1 = 4 -2=2, \\ n = 5 \\ an = a1 + d × (n - 1) \\ a5 = 2 + 2 × (5 - 1) =10 \\ S5 = \frac{2 + 10}{2} \times 5 \\ S = 30$