Question

−1, k and −1 are three consecutive terms of a G.P., then 

1. k = 1 
2. k = −1 

Which of the following is valid?

Options

• only 1

• only 2

• both 1 and 2

• either 1 or −1

Answer 1

either 1 or −1

Explamation:

Given,

−1, k and −1 are three consecutive terms of a G.P.

∴  `k/(−1) = −1/k`

⇒ k × k = −1 × −1

⇒ k² = 1

⇒ k = 1

= ±1.