Question

for an A.P. a =6 and S10 =195 Show that Sn -3:Sn-8=n(n -3) :(n -5) (n -8)

Answer 1

Sn = n/2[2a +(n-1)d]
S10= 10/2[2*6 +9d]
after solving this,value of d=3.
now,
Sn-3=(n-3)(3n)/2
Sn-8=(n-8)(3n-15)/2