Question

which term of an ap 24 ,21 ,18 ,15 ....is tthe 1st negative term???

Answer 1

a=24.   d=21-24=-3

an<0

a+(n-1)d<0

24+(n-1)-3<0

24-3n+3<0

27<3n

27/3<n

9<n

the next term from 9 is 10.....so 10th term is first negative term

hope it helped......☺️

Answer 2

In the given AP :-
24 , 21 , 18 , 15 , .........
First term , a = 24
Common difference , d = 21 - 24 = -3

Now the first negative term can be expressed as a + (n - 1) d < 0
→ 24 + (n - 1) (-3) < 0
→ (n - 1)(-3) < -24
→ -3n + 3 < -24
→ -3n < -24 -3 = -27
→ 3n > 27
→ n > 27/3
→ n > 9
Therefore , the 10th term of the AP will be its first negative term .

Hope it helps !