Question

if 3rd term of AP is 1 and 6th term is -11 find the sum of its 32 term

Answer 1

x3=1
first term=f
common difference=d
f+2d=x3
f+2d=1...(1)

x6=f+5d
-11=f+5d
f+5d= -11 ...(2)

(1)-(2)

f+2d=1-
f+5d= -11
---------------
12=-3d
d= 12/-3= -4
f+2d= -1
f-8=-1
f=7

sn=[tex] \frac{n}{2}[2f+(n-1)d] \\ \\ \frac{32}{2}[-14+ 31*-4) \\ \\ 16(-14-124) \\ \\ 16(-138) =−2208[/tex]

Answer 2

please look at these attachments.