Question

find the 12th term from the end of the A. P - 2,-4,-6,..........,-100

Answer 1

a = -2
d = -2
t12 = -2 + 11 * -2
= -24
please comment if you have any doubt

Answer 2

first calculate the no. of terms by
a(n)=
$a + (n - 1)d$
so no. of terms will 18
to find term from last formula is
$(n - r + 1) {th}^{term}$
so now the term which you have to give from last now you got its place from start
now it gives you 7th term from starting which is 12th term from last
now find it by applying a(7)
$a + (6 - 1)d$
now you get
a(n)=2+(6)-6
a(n)=-34