Question

Find the sum of 51 terms of an ap whose second terms is 2 and 4th terms is 8

Answer 1

a2=2=>a+d=2.....(i)
a4=8=>a+3d=8.....(ii)
Subtracting
-2d=-6
d=3
a3=a2+d=>2+3=5
a=a2-d=2-3=-1
Now,
n=51
S51=n/2(a+50d)
=51/2(-1+150)

Answer 2

A2= 2 or a+d=2
A4=8 or a+3d=8
By elimition method
=-2d=-6d
D=3

A+3=2
A=-1

A51=a+50d
-1+3*50
-1+150
149

Hope this helps u
Plzz give brainliest if answer was helpful to u