SOLUTION: Write a rule for the nth term of the arithmetic sequence that has the 2 given terms. A(20)=240, A(15)=170 I understand how to write a rule for a sequence using the A(n)=A(1)

Question 378345: Write a rule for the nth term of the arithmetic sequence that has the 2 given terms.
A(20)=240, A(15)=170
I understand how to write a rule for a sequence using the A(n)=A(1)+(n-1)d, but I do not understand how to get a rule without having the first term and common difference. Any help is really appreciated!
Thanks so much!
Answer by scott8148(6628) (Show Source): You can put this solution on YOUR website!
you have the formula

how many differences between A(15) and A(20)?
what's the numerical difference between the terms?

5d = 240 - 170

plug the value of d into your formula to find A(1)
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