Question

Step by step explanation of 21, 18 , 15,....is term of an AP is -81

Answer 1

a = 21

d = -3

An = a+(n-1)d

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

so,

n = 35

Answer 2

a=21

d=18-21 =-3

an=-81

an=a+(n-1) d

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

-81=21+3-3n

-81=24-3n

-105=-3n

n=35

The 35th term of a.p is -81

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