diketahui barisan aritmatika 3,2x,13 Berapakah nilai U 20?

U1 = a = 3
U2 = 2x
U3 = 13

beda
13-2x = 2x - 3
13 + 3 = 2x + 2x
16 = 4x
x = 16/4
x = 4

b = 2 × 4 - 3
b = 8 - 3
b = 5

U20 = 3 + (20-1) 5
U20 = 3 + 19 × 5
U20 = 3 + 95
U20 = 98

Jadi, nilai U20 = 98