Question

20th term from the last term of the ap 21,18,15. -72 is​

Answer 1

Answer:

a20=a+(n-1)d

write the ap in reverse order-72.15,18,21

a20=-72+(20-1)-3

=-72-57

=-129

Answer 2

Answer:-

-15

step by step explanation:-

According to the question to find the last 20th term ,

let us take the AP in reverse so

-72,...........,15,18,21is the AP now

here a=-72,d=3,n=20,an=?

an=a+(n-1)d

an=-72+(20-1)3

an =-72+19×3

an =-72+57

an =-15

thus,-15 is the last 20th term from last