Question

the 9th term of an ap is -37 and the sum firt 6 terms is - 27 . find the sum of its first eight terms​

Answer 1

answer- A9= -37 S6= -27 S8=?

NOW , A9= A+ 8d so,

-37=A+8d

A=-37-8d ----(i)

now ,

S6=-27 NOW

6/2(2×-37-8d+(5)d)=-27

3(-74-16d+5d)=-27

-74-11d=-27/3=-9

-11d=-9+74

d= -65/11 ----(ii)

now put ---ii in equition --i

so we have , A= -51

S8 = 4(-102+(7)-65/11)

=4(-102-455/11)

4×-143.36

= -573.5 aprrox is valve of S8