If the 4th, 10th and 16th terms of a G.P. are x, y and z respectively, prove that x, y, z are in G.P.

15, 30, 60, 120 …… are in G.P. (Geometric Progression).

(a) Find the nth term of this G.P. in terms of n.

(b) How many terms of the above G.P. will give the sum 945 ?

The roots of the equation (q - r)x² + (r - p)x + (p - q) = 0 are equal.

Prove that : 2q = p + r, that is, p, q and r are in A.P.