diketahui barisan aritmatika dengan U10=32 dan U21=65 tentukan U75

Barisan Aritmetika.

a + 9b = 32
a + 20b = 65
__________ -
-11b = -33 → b = 3
a + 9(3) = 32 → a = 5

Un = a + (n - 1)b
U₇₅ = 5 + (75 - 1)(3) = 227

U21 = a + 20b = 65
U10 = a + 9b = 32
______________ -
. 11b = 33
. b = 3


U10 = a + 9b = 32
a + 9(3) = 32
a = 32 - 27
a = 5


U75
= a + 74b
= 5 + 74(3)
= 5 + 222
= 227