diketahui barisan aritmatika u3=10 u7=21 tentukan u10 mohon dijawab

U3 = 10
a + 2b = 10
U7 = 21
a + 6b = 21

a + 2b = 10
a + 6b = 21
_________ _
-4b = -11
b = -11/-4
b = 2,75

a + 2b = 10
a + 2(2,75) = 10
a + 5,5 = 10
a = 10 - 5,5
a = 4,5

U10 = a + 9b
= 4,5 + 9(2,75)
= 4,5 + 24,75
= 29,25