Diketahuu barisan aritmatikadengan u3 =11 dan u15 =59, tentukan besar u10

U11 = a + 2b
U15 = a + 14b

Maka,
a + 2b = 11
a + 14 b = 59. -
-12b = -48
b = 4

a + 2b = 11
a + 2(4) = 11
a + 8 =11
a = 3

Maka, U 10
= a + 9b
= 3 + 9(4)
= 3 + 36
= 39

u3 = a + 2b = 11
u15 = a + 14b = 59

kita eliminasi

a + 2b = 11
a + 14b = 59
........................... -
- 12 b = - 48
b = 4

kita cari a
dengan substitusi ke u 3 / u 15
u 3 = a + 2b
11 = a + 2(4)
11 = a + 8
a = 3

kita substitusi nilai a dan b ke u 10
u 10 = a + 9b
= 3 + 9(4)
= 3 + 36
= 39