A(n) =2+9(n-1)= 2 + 9n - 9= 9n -7
A(n-1)= 2+9[(n-1)-1]= 2 + 9(n-2)= 2+ 9n - 18= 9n -16
A(n)- A(n-1)= (9n-7)-(9n-16) = -7+16=9
A(n)= A(n-1) +9 is the answer
