(Q3).Determine the AP whose 3rd term is 5 and the 7th term is 9.

We have

an = a + (n - 1)d

a3 = a + ( – 1) d = a + d = ......(1)

and a7 = a + ( – 1) d = a + d = .....(2)

Solving the pair of linear equations (1) and (2), we get

a = , d =

Hence, the required AP is , , , , , . . .