Asked by HENRY

THE 10TERM OF AN AP IS -27 AND THE 5TH TERM IS -12 WHAT IS THE 18th term find also the sum of its 25TERM
Answered by oobleck
a+9d = -27
a+4d = -12
Solve for a and d, then find
T18 = a+17d
S25 = 25/2 (2a + 24d)