Question

The sum of first n terms of AP is given by Sn = 2n3+3n. Find the sixteenth term of the AP

Answer 1

sn = 2n^3 +3n
n=1
s1= 2 +3 =5=a1
s2= 2 x 2^3 +6= 20
s2=a1+a2
20= 5+a2
a2=15
d=15-5=10
a16=a+15d
a16=5 +150=155
16th term of an ap is 155