The fifth term of an arithmetic sequence is 9 and the 32nd term is -84. What is the 23rd term?
9 = 4 D + F
-84 =31D + F
F=205/9 First term
D=-31/9 Common difference
23rd =205/9 + (23 -1)*(-31/9)
23rd = -53 The 23rd term.
