SOLUTION: The first three terms of an arithmetic sequence are 2x-1;3x;5x-2........i found x as 3...calculate the sum of the first 21 terms of the sequence
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Question 877252: The first three terms of an arithmetic sequence are 2x-1;3x;5x-2........i found x as 3...calculate the sum of the first 21 terms of the sequence Answer by richwmiller(17219) (Show Source):
You can put this solution on YOUR website! 2x-1;3x;5x-2
5x-2-3x=3x-(2x-1)
x=3
S = ½(2a + (n-1)d)n
5*3-2=13
3x=9
13-9=4
d=4
2x-1=6-1=5
S = ½(10 + 4(20))21
S = ½(90))21
S=45*21
S=945
