Let the first term be a and the common ratio be R.

∴ According to the question,

a_p = x.

a_q = t

a_r = z.

We know that a_n = aR^n-1

∴ a_p = aR^p-1= x

a_q = aR^q-1= y

a_r = aR^r-1= z

⇒ x^q-r = (aR^p-1)^q-r

⇒ y^r-p = (aR^q-1)^r-p

⇒ z^p-q = (aR^r-1)^p-q

Multiplying the above three equations we get

x^q-r.y^r-p.z^p-q = (a^q-r.R^pq-pr-q+r). (a^r-p.R^rq-pq-r+p). (a^p-q.R^pr-qr-p+q)

=(a^q-r+r-p+p-q.R^{pq-pr-q+r+rq-pq-r+p+pr-qr-p+q})

= (a⁰.R⁰)

= 1.