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
Algebra.Com
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
RELATED QUESTIONS
the first three terms of an arithmetic projection are x,2x+1 and 5x+1.find x and the sum... (answered by ikleyn)
2x-4;x+5 and 3x-1 are the first three terms of an arithmetic sequence.(I) show that x=5... (answered by ikleyn)
The first three terms of an arithmetic sequence, in order, are 2x + 4, 5x – 4, and
3x +... (answered by edjones,Edwin McCravy)
The first three consecutive terms of an exponential sequence are (x-1), 2x and (5x+3)... (answered by greenestamps)
The sum of the first n terms of an arithmetic squence is given by the formula; Sn= n/2... (answered by edjones)
The three consecutive terms of exponential sequence are x-1,2x&5x+3,find(1)x(2) find... (answered by greenestamps)
The three consecutive terms of exponential sequence are x_1,2x,&5x+3,find (1)x(2) find... (answered by ikleyn)
x,2x+1,11 are three consecutive terms of an arithmetic sequence. Calculate(i) x.(ii) the... (answered by math_helper)
The first two terms of a geometric sequence and an arithmetic sequence are the same. The... (answered by Edwin McCravy)