The sum of the first n terms of an AP is (3n² + 5n). Which term of the AP is 152?

sum of first term=S₁=a₁

s₁=3*1²+5*1=3+5=8

s₂=a₁+a₂

s₂=3*2²+5*2=3*4+10=12+10=22

so, a₂=s₂-s₁

22-8=14

so ap is 8,14.......d=14-8=6

now a_n=152

a_n=a+(n-1)d

152=8+(n-1)6

152-8=(n-1)6

144/6=n-1

24=n-1

25=n

so 25^th term

.Hope u got it!!!!