f(9) = f(8)+3
f(8)=f(7)+3
f(7)=f(6)+3
f(6)=f(5)+3
f(5)=f(4)+3
f(4)=f(3)+3
f(3) = f(2)+3
f(2) = f(1)+3
f(2)=4 f(3)=7 f(4)=10 f(5) = 13 f(6) = 16 f(7)=19 f(8) = 22 f(9)=25
13. 若 f(1)=1, f(n)=f(n-1)+3,則 f(9)=? (A..-阿摩線上測驗