Question

find 18th term from the last term of the of the AP 10,7,4..........-80​

Answer 1

18th term from last of AP 10,7...-80 = 18th term from first of AP: -80...7,10

now In AP: -80...7,10

a1 = -80

d = 10 - 7 =3

now a18 = a + 17d

a18 = -80 + 17 x 3

a18 =  -80 + 51

a18 = -29

therfore 18th term from last of the AP  10,7,4..........-80 is -29

Answer 2

Step-by-step explanation:

AP=10,7,4..........-80

reverse this

AP= -80,-77,-74..........4,7,10

first term(a)= -80

common difference(d) = 2nd term - first term

= -77-(-80)

= 3

A(18term)= a+(n-1)xd

=-80+(18-1)x3

= -80 + 17 x 3

= -80 + 51

= - 29

18 term is -29