Question

if sn the sum of first n term of an ap is given by sn is = 3n square -4n
then find its nth term

Answer 1

sn=3n^2-4n
S1=-1
S2=4
S3=15
T1=S1=-1
T2=s2-s1
T2=5
T3=s3-s2
T3=11
a=-1 , d=5
tn= a+(n-1)d
=-1+(n-1)5
tn= -1+5n-5
tn=5n-6