Question

which term of an ap is21,18,15... is -81

Answer 1

a = 21

d = - 3

Tn = - 81

=> a +(n-1)d = - 81

=> 21 + (n-1)(-3) = - 81

=> (n-1)(-3) = - 102

=> n-1 = 34

=> n = 35

The 35th term of given AP is - 81

Answer 2

we have given that a=21 , d=a2-a3=-3. an=81
we know that an=a+(n-1)d
-81 =21+(n-1)-3
-81-21=(n-1)-3
-102=(n-1)-3
34=n-1
n= 35
35th term of the ap is -81
Hope! You could help.