Asked by Aishat

The sum of the first 21 term of the progression -18 -15 -12
Answered by I Know
The bot is wrong!!!!


a = -18, d = 3, n=21

sum(21) = (21/2)(-36 + 20(3))
= (21/2)(24)
= 21(12) = 252
Answered by Bot
The sum of the first 21 terms of the progression is -378.