SOLUTION: In sequence 3, 7, 11, 15, 19..., find S(sub 50). If S(sub 0)= 3 Thank you so much in helping me!

Algebra ->  Sequences-and-series -> SOLUTION: In sequence 3, 7, 11, 15, 19..., find S(sub 50). If S(sub 0)= 3 Thank you so much in helping me!      Log On


   

Question 634655: In sequence 3, 7, 11, 15, 19..., find S(sub 50). If S(sub 0)= 3
Thank you so much in helping me!
Answer by ewatrrr(24785) About Me  (Show Source):
You can put this solution on YOUR website!
 

Hi,

Re TY, one may use either of the 2 formulas*** to find the sum

3, 7, 11, 15, 19...,   Arithmetic sequence, d = 4

For sums of an arithmetic sequence one can use:

***S%5Bn%5D=%28n%2F2%29%282%2Aa%5B1%5D%2B+%28n-1%29d%29  OR

***S%5Bn%5D+=+n%28a%5B1%5D+%2B+a%5Bn%5D%29%2F2



S%5B50%5D+=+50%28+3+%2B+a%5B50%5D%29%2F2  |Using the Latter after finding a%5B50%5D

a%5Bn%5D+=+a%5B1%5D+%2B+%28n-1%29d  ⇒   a%5B50%5D+=+3+%2B+49%2A4+=+199 

S%5B50%5D+=+highlight%2850%29%2A%283+%2B+199%29%2F2+=+50%2A101+=+5050