Question

find the sum of first 20 terms of the ap .. √2,√8,√18..... also find its nth term

Answer 1

A.P.=√2,√8,,√18.............
=√2, 2√2, 3√2,..............
In an A.P.
an=a+(n-1)d
Here,n=20
a=√2
d=√2
an=√2+(20-1)√2
an=√2+19√2
an=20√2
Therefore, the an term of the A.P. is 20√2.
Sum of 20 terms of the A.P. IS
Sn=n/2[a+an]
Here,we have to find S20
a=√2
an=20√2
n=20
S20=20/2[√2+20√2]
=10[21√2]
=210√2