f(x) = 9x + 3

f(x) = 3x + 12

f(x) = 3x + 9

f(x) = 1x + 12

a_n=a_n-1 + 8

a_n=a_n-1 + 5

a_n=a_n-1 + 3

a_n=a_n-1 + 1

$$f(n)=-5+60n$$

$$f\left(n\right)=-5n+55$$

$$f\left(n\right)=-5n+65$$

$$f\left(n\right)=5n+55$$

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