Question

give step wise answer plz

Answer 1

these are at all............
we needs...
1)s1 =a
2)s2-s1 = a
3)s3-s2= a2

Answer 2

Given 3n + n^2

N=1 :-
3(1) + (1)^2 = 4 (t1)


N=2:-
3(2) + (2)^2 = 6+4 = 10


t2 = 10-4 = 6 is the second term !


D = 6-4 = 2 ( 4 is the first term )

Sum of first two terms is 6 ! ( n/2 = 2/2=1)


Therefore we found !

t3 = a+2d = 4+2(2) = 8

t15 = a+14d = 4+14(2) = 32

Hope it helps ..