The sum of the first ten terms of a linear sequence is -60 and the sum of the first fifteen terms of -165. Find the 18th term of the sequence
The 18th term of the sequence = -225
AAAaannndd the bot gets it wrong yet again!
10/2 (2a+9d) = -60
15/2 (2a+14d) = -165
a = 3, d = -2 so
a+17d = 3-34 = -31