Question

Which term of AP 21 , 18, 15, ............. is -81 ?also is an term 0 Give reason for your answer ??????

Answer 1

yes this an arithematic progression ...
a=T1=21
T2=18
T3=15 ...thus the value of d ( comman difference)= is -3 ....(18-21)...(15-18)... .
the 0 is the 8 the term in this ap

Answer 2

Answer:

Here, a = 21,

d = 18 – 21 = – 3

and

an = – 81, and we have to find n.

As an = a + ( n – 1) d,

we have;

– 81 = 21 + (n – 1)(– 3)

– 81 = 24 – 3n

– 105 = – 3n

So, n = 35

Therefore, the 35th term of the given AP is – 81.

Next, we want to know if there is any n for which an = 0.

If such an n is there, then;

21 + (n – 1) (–3) = 0,

3(n – 1) = 21

n = 8

Therefore, the eighth term is 0.