Question

which term of an ap 21 18 15 ........is -18

Answer 1

$here \: is \: your \: answer$

$a_{n} = - 18 \\ a = 21 \\ d = - 3 \\ a_{n} = a + (n - 1)d \\ = > - 18 =21 + (n - 1) - 3$

$= > - 39 = (n - 1) - 3 \\ = > \frac{ - 39}{ - 3} = n - 1 \\ = > 13 = n - 1 \\ = > n = 14$

$plz \: mark \: as \: brainlist$

Answer 2

a = 21

d = -3

Term of an AP

a(n)= a +(n-1) *d

-18 = 21 + (n-1) * -3

-18 -21 = (n-1) *-3

- 39 = (n - 1) * -3

-39/-3 = ( n-1 )

13 = n-1

14 = n

It is fourteenth term

hope it helps please mark brainliest :-) :-) :-)