Question

If 11, a, b, 2, are in A.P., find the values of a and b.

Answer 1

a₁ = 11

a₂ = 2

a_n = a₁ + (n − 1)d

2 = 11 + (4 − 1)d

2 = 11 + 3d

2 − 11 = 3d

− 9 = 3d

d = `(-9)/3`

d = −3

Calculate the values of a and b:

a = a₁ + d

=11 + (−3)

= 8

b = a + d

= 8 + (−3)

= 5