Question

can anyone answer the 13th one

Answer 1

This is the answer for ur question....

Answer 2

Given that sum of n terms of an AP sn = 3n^2 + 5n.

Then, 

s1 = 3(1)^2 + 5 * 1

    = 3 + 5

    = 8.


s2 = 3(2)^2 + 5 * 2

     = 12 + 10

     = 22.


Therefore first term a1 = 8 and second term a2 = 22. 

d = a2 - a1

   = 22 - 8

   = 14.


Therefore the AP is 8,14,20,26,.....


Now,

We know that nth term of an AP an = a + (n - 1) * d

Then, 15th term a15 = 8 + (15 - 1) * 14

                                  = 8 + 14 * 14

                                  = 204.


Hope this helps!