Yang C no 1.S25 Tolong bantuin sayaa besok di kumpulkan

1.)
4 + 9 + 14 + ...
a = 4
b = 9-4 = 5

a) Un = a + (n-1)xb
U10 = 4 + (10-1)x5
= 4 + 9x5
= 4 + 45 = 49

b) Sn = n/2 (2a + (n-1)xb)
S20 = 20/2 (2x4 + (20-1)x5)
= 10x(8 + 19x5)
= 10x(8 + 95)
= 10x(103)
= 1030

c) S berapa ?

2.) deretnya mana ??