Determine the AP whose fifth term is 19 and the difference of the eighth term from the thirteenth term is 20.

Question

Philoid · Accepted Answer

Let the first term of an AP be a and common difference d.

Given

5^th term, a₅ = 19

And by using the nth term formula i.e. a_n = a + (n - 1)d

a + 4d = 19

a = 19 - 4d (eqn 1)

also,

20^th term - 8^th term = 20

a + 19d - (a + 7d) = 20

12d = 20

using this in eqn 1

So the AP is