Question

find sum af first 12 terms of AP, - 37, -33, -20,​

Answer 1

a = -37

d = +4

n = 12

general term, an = a + (n-1)d

-37 + 4n - 4 = 4n - 41

12

Ʃ (4n-41) = n/2 (a + a12)

n = 1

there fore,

6 × (-37 + 7)

6 × -30

-180