Dua suku berikutnya dari barisan 2,7,9,16,25,.....

a = 2
b = 7-2
= 5

un = a+(n-1)b

U6 = 2+(6-1)5
= 2+(5).5
= 2+25
= 27

U7 = 2+(7-1)5
= 2+(6).5
= 2+30
=32