If a, b, c are in G.P. and x, y are the arithmetic means of a, b and b, c respectively,
then prove that and
Given a, b, c, d are in G.P.
b = ak, c = bk, d = ck or b = ak, c = ak2, d = ak3 ...(1)
Given a, b are roots of equation
a + b = 3, ab = p [By using (1)]
a + ak = 3, a. ak = p
a(1 + k) = 3 ...(2)
and ...(3)
Also, c, d, are roots of equation
c + d = 12, cd = q
or [By using (1)]
...(4)
and ...(5)
Dividing (4) by (2), we get
...(6)
Consider
Applying componendo and dividendo, we get or (q + p) : (q - p) = 17 : 15.