1.

For A.P 21,18,15....... check which term is -27?

Answer»

Step-by-step explanation:

Given -

AP = 21, 18, 15, ......

an = - 27

To FIND -

Which term is - 27 ?

Now,

21, 18, 15, .......

here,

a = 21

d = 18 - 21 = - 3

an = - 27

Now,

  • an = a + (N - 1)d

= - 27 = 21 + (n - 1)-3

= - 27 - 21 = - 3n + 3

= - 27 - 21 - 3 = - 3n

= - 51 = - 3n

= n = -51/-3

  • = n = 17

Hence,

17th term of the AP is - 27.

Formula USED -

  • an = a + (n - 1)d


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