SOLUTION: Hi, can anyone help me with these two questions on series and sequences?: 1) For the sequence 15,12,9,... find the common difference and the nth term. 2) If 3x-1, 2x+2 and 2x

Algebra ->  Sequences-and-series -> SOLUTION: Hi, can anyone help me with these two questions on series and sequences?: 1) For the sequence 15,12,9,... find the common difference and the nth term. 2) If 3x-1, 2x+2 and 2x      Log On


   



Question 426924: Hi, can anyone help me with these two questions on series and sequences?:
1) For the sequence 15,12,9,... find the common difference and the nth term.
2) If 3x-1, 2x+2 and 2x-1 are in Arithmetic Progression, find value of x.
Thank you for your time and consideration!

Answer by Gogonati(855) About Me  (Show Source):
You can put this solution on YOUR website!
Solution: 1)The common difference is d=12-15=9-12=-3 and the nth term is:
a%5Bn%5D=a%5B1%5D-%28n-1%29d
a%5Bn%5D=15-%28n-1%293, simplify the formula
a%5Bn%5D=18-3n.
2)Since the sequence: 3x-1, 2x+2, 2x-1 is an arithmetic progression we have:
(2x+2)-(3x-1)=(2x-1)-(2x+2) => -x+1=-3 => x=4.