Question

Find a₃₀ − a₂₀ for the A.P.

−9, −14, −19, −24, ...

Answer 1

In this problem, we are given different A.P. and we need to find `a_30 - a_20`.

A.P. −9, −14, −19, −24, ...

Here

First term (a) = -9

Common difference of the A.P. (d) = - 14 - (-9)

= -14 + 9

= -5

Now as we know

`a_n = a + (n -1)d`

Here we find `a_30` and `a_20`

So for 30 th term

`a_30 = a + (20 - 1)d`

`= -9 + (19)(-5)`

= -9 - 95

= -104

So

`a_30 - a_20 = -154 - (-104)`

=-154 + 104

= -50

Therefore for the given A.P `a_30 - a_20 = -50`