# SOLUTION: I'm supposed to find the specific term of each arithmetic sequence. The problem is : t1=5, t3=20; and I need to find t subscript 12. I can use the equation tn=t1+(n-1)d if that he

Algebra ->  Algebra  -> Sequences-and-series -> SOLUTION: I'm supposed to find the specific term of each arithmetic sequence. The problem is : t1=5, t3=20; and I need to find t subscript 12. I can use the equation tn=t1+(n-1)d if that he      Log On

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 Question 603294: I'm supposed to find the specific term of each arithmetic sequence. The problem is : t1=5, t3=20; and I need to find t subscript 12. I can use the equation tn=t1+(n-1)d if that helps you any? Thanks for the help.Answer by htmentor(788)   (Show Source): You can put this solution on YOUR website!The n-th term of the arithmetic sequence is written t_n = t1 + (n-1)d where d = the common difference and t1 is the 1st term So we need to find d We can form two equations for the common difference d = t2 - t1 = t2 - 5 d = t3 - t2 = 20 - t2 Add the two equations together: 2d = 15 -> d = 7.5 Therefore, t12 = 5 + 7.5(12-1) t12 = 87.5