SOLUTION: The first three terms of an arithmetic series are 60, 4p and 2p � 6 respectively. Show that p = 9 Find the value of the 20th term of this series. Prove that the sum of the

Question 940801: The first three terms of an arithmetic series are 60, 4p and 2p � 6 respectively.
Show that p = 9
Find the value of the 20th term of this series.
Prove that the sum of the first n terms of this series is given by the expression
12n (6 � n)
Answer by josgarithmetic(39625) (Show Source): You can put this solution on YOUR website!
Difference between successive terms is a constant.

The three terms are: 60, 36, 12
Common difference is .

General term, .
n is the index for the term.

The general term is usually stated as , but you know from your specific example that d=-24, so subtraction is shown for the general term of your example. You would evaluate .
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