Question

the sum of n terms of an AP =n² +3n. Find its 14th​

Answer 1

Step-by-step explanation:

if in an AP sum of terms is given in a quardratic form like an²+bn+c then d= 2a

here d= 2×1=2

a14=a+2(14-1)=a+26

in any AP S1=a1=1+3=4

a14= 4+26=30