Question

Diketahui barisan aritmatika U5=22 dan U10=42 .Suku ke-25 barisan tersebut adalah...

Answer 1

U5 = a+4b = 22
U10= a+9b = 42
------------------- -
-5b = -20
b= -20/-5
b = 4

a+4(4) = 22
a+16 = 22
a = 22-16
a= 6

Un = a+(n-1)b
U25= 6+(25-1)4
U25= 6+24.4
U25= 6+96
U25 = 102

Answer 2

U5 = a + 4b = 22
U10= a + 9b = 42
__________________ --
-5b = -20
b = 4

a + 4b = 22
a + 4(4) = 22
a = 22-16
a = 6

U25 = a + (n-1)b = 6 + 24(4) = 6 + 96 = 102

jadi suku ke-25 barisan tersebut adalah 102