Question

If k − 1, k + 1 and k + 5 are in G.P. then the value of k is ______.

Options

• 2

• 3

• 4

• 1

Answer 1

If k − 1, k + 1 and k + 5 are in G.P. then the value of k is 3.

Explanation:

a = k − 1

b = k + 1

c = k + 5

(k + 1)² = (k − 1)(k + 5)

k² + 2k + 1 = k² + 5k − k − 5

k² + 2k + 1 = k² + 4k − 5

2k + 1 = 4k − 5

1 + 5 = 4k − 2k

6 = 2k

k = `6/3`

k = 3