Find the 13th term of the arithmetic sequence whose common difference is =d−7 and whos first term is =a13.

Question

Find the 13th

 term of the arithmetic sequence whose common difference is =d−7

 and whose first term is =a13

.

Answer 1

1st term = a13

common difference = d-7

nth term = an = a1 + d(n-1)

a13 = a13 + (d-7)(n-1) = a13 +(d-7)(13-1) = a13 +(d-7)(12) = a13 +12d -84

12d-84 = 0

12d = 84

d =84/12 = 7

13th term = the 1st term = a13

at least that's one possible interpretation of the problem with corresponding solution.

UNLESS you copied the problem wrong, or the problem itself was a misprint, which is very likely