Tolong Jawab ya, dikumpul sekarang

f(n) = 2n - 1 + 2n - 2n + 1
f(n) = 2n

f(1) + f(2) + f(3) + f(4) + f(5)
= 2 + 4 + 6 + 8 + 10
= 30
atau

a = 2
b = 4 - 2 = 2
n = 5

Sn = n/2(2a + (n - 1)b)
S5 = 5/2(2(2) + (5 - 1) × 2)
S5 = 5/2(4 + 4 × 2)
S5 = 5/2(4 + 8)
S5 = 5/2(12)
S5 = 30

catatan : tidak ada pilihan