Question

Sum to n terms of arithmetic progression is 2n^2+n then eighth term is

Answer 1

Answer:

a8=31

Step-by-step explanation:

sn=2n^2+n

s1=a1

2(1)^2+1=a1

2(1)+1=a1

3=a1

s2=a1+a2

2(2)^2+2=3+a2

2(4)+2=3-a2

8+2-3=a2

7=a2

d=a2-a1

d=7-3

d=4

an=a+(n-1)d

a8=3+7(4)

a8=3+28

a8=31  

a8 is 31