find the nth term of the following AP

Question

a, 3,7,11,.. .

Answer 1

d = 7 - 3 = 4
or
d = 11 - 7 = 4
whew the same
term 1 = a = 3 -4 = -1
so
-1 , 3 , 7, 11, .....
-1 + (n-1)* 4