Question

The 9th term of an arithmetic progression is 8 and the 4th term is 18.

Find the 1st term and the common difference, d.

Answer 1

a = 24 and d = -2

Explanation:

The 9th term = a + 8d

the 4th term = a + 3d

from the question it is given that

a + 8d = 8----------(1)

a + 3d = 18---------(2)

Solve the two equations simultaneously we will be a = 24 and d = -2