Jika u3=24 u8=54 tentukan u13

Rumus baris aritmatika
Un = a + (n-1) b

U3 = a + (3-1) b
24 = a + 2b

U8 = a + (8-1) b
54 = a + 7b


54 = a + 7b
24 = a + 2b
----------------- -
30 = 5b
b = 6

U8 = a + (8-1) 6
54 = a + 42
a = 12

a = 12
b = 6

U13 = 12 + (13-1) 6
= 12 + 72
= 84

U13 = 84