Question

find the sum of 16 terms of an a. P - 1, - 5 - 9,​

Answer 1

sn=n\2[2a+(n-1)d]

S16=8[-2+-60]

=-496

Answer 2

Answer:

a=-1

d = -5-(-1)

=-4

n= 16

s=n/2(an+a)

an=a+(n-1)d

a16= -1+(16-1)-4

= -1-60

=-61

s=16/2(-61-1)

=8*-62

=-496