Jika u3+u7=56 dan u6+u10=86 tentukan suku ke5 adalah

U3 + U7 = 56
a + 2b + a + 6b = 56
2a + 8b = 56
a + 4b = 28

U6 + U10 = 86
a + 5b + a + 9b = 86
2a + 14b = 86
a + 7b = 43

a + 4b = 28
a + 7b = 43
_________ _
-3b = -15
b = -15/-3
b = 5

a + 4b = 28
a + 4(5) = 28
a + 20 = 28
a = 28-20
a = 8

U5 = a + 4b
= 8 + 4(5)
= 8 + 20
= 28