17. The sum of n terms of an AP is 3n2 +5m. Find the AP Hence, find it

1.	17. The sum of n terms of an AP is 3n2 +5m. Find the AP Hence, find its 15te5 teril.l1 and R nre2-2) and (2-4) respectively, find the co-ordin(2,
Answer» The sum of n terms of an A.P. = 3n^2+5n then sum of n-1 terms= 3(n-1)^2+5(n-1) So nth term of A.P will be Tn=3n^2+5n- 3(n-1)^2-5(n-1)= 3n^2+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, nHence n=15hence6*15+2=90+2=92

17. The sum of n terms of an AP is 3n2 +5m. Find the AP Hence, find its 15te5 teril.l1 and R nre2-2) and (2-4) respectively, find the co-ordin(2,

Answer»

The sum of n terms of an A.P. = 3n^2+5n

then sum of n-1 terms= 3(n-1)^2+5(n-1)

So nth term of A.P will be Tn=3n^2+5n- 3(n-1)^2-5(n-1)= 3n^2+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, nHence n=15hence6*15+2=90+2=92