Question

sum of n terms=n square. What is the value of a20

Answer 1

Sn=n2
an=Sn-Sn-1
an=n2-(n-1)2
=n2-{n2+1-2n}
=n2-n2-1+2n
=2n-1

an=2n-1
as n=20...
2(20)-1
=40-1
=39..
Hence the value of the 20th term is 39..
hope this helps!!
cheers!! (:

Answer 2

s1=a1= n^2. a1= 1^2. a1=1. a1=s2-s1. s2= 2^2. s2= 4. a2=4-1. a2=3. d=2. a20= a+(n-1)d. a20=1+ 19×2. a20= 39