Question

Which term of the ap 24,21,18.... is the first negative term?.

Answer 1

Heya !!



Let nth term of the given AP be the first negative term.




AP = 24 , 21 , 18



Here,



First term ( a ) = 24



Commmo difference ( d ) = 21-24 = -4.




Then , Tn <0



=> { a + ( n - 1 ) × d } <0




=> { 24 + ( n - 1 ) × -3 } <0




=> 27 - 3n <0



=> 27 < 3n




=> 3n > 27



=> n = 9.


n = 10

Hence,


The 10th term is the first negative term of the given AP.

Answer 2

The given A.P. : 24,21,18….

a= 24

d= -3

n=?

Let us first find which term will be 0.

Using the formula : an= a+(n-1)d

0=24-(n-1)(-3)

24–3n+3=0

n= 9

So 9th term will be 0. Hence 10 term will be first negative. Again using the same formula where n= 10, we get,

An= 24+9(-3)=-3

Hence first negative term is -3.