Question 1123342
.


The r-th term is the difference between the first r terms and the sum of the first (r-1) terms, i.e.


a[r] = (5*r^2-2*r) - (5*(r-1)^2-2*(r-1)) = 


           = 5r^2 - 2r - 5r^2 + 10r - 5 + 2r - 2 = 10r - 7.


Answer.  10r - 7.  Options b).


i got the answer from https://www.algebra.com/algebra/homework/word/misc/Miscellaneous_Word_Problems.faq.question.1123342.html