Question

the sum of the first 'n' terms of an AP is 3n2+5n.write AP hence find its 16th term.

Answer 1

hello

The sum of n terms of an A.P. = 3n²+5n

then sum of n-1 terms= 3(n-1)²+5(n-1)

So nth term of A.P will be Tn=3n²+5n- 3(n-1)²-5(n-1)=
3n²+5n-3n²-3+6n-5n+5=6n+2

in this way by putinng values of n= 1,2,3,4,5,6,7,_______n-1, n

we will get the AP as 8,14,20,26,32,38,44,____and the 16th term will be= 6*16+2=98

hope its help you dude