Question

The first term of an ap is - 7 and the common difference 5,find its 18th term and General term

Answer 1

a = - 7
d = 5

T18 = a + 17d
= - 7 + 17*5
= - 7 + 85
= 78

General term = a +(n-1)d
= - 7 + (n-1) 5
= - 7 + 5n - 5
= 5n - 12

Answer 2

Hello......................
a= -7 
d=5
 
Then its 18th term
   a18= a+[n-1]d
   a18= -7+[18-1]5
   a18= -7+17×5
   a18= -7+85
   a18= 78

General term 
an=a+[n-1]d
    = -7 + [n-1]5
    = -7 + 5n - 5
    = 5n - 12