The product of three numbers in G.P. is 125 and the sum of their products taken in pairs is Find them.
The sum of three numbers in G.P. is 21 and the sum of their squares is 189. Find the numbers.
Let a, ar, ar2, ar3 be the four numbers in G.P.
Since the third number is greater than the first by 9
∴ ar2 = a + 9 a(r2 - 1) = 9 ...(i)
Since the second number is greater than the fourth by 18
∴ ar = ar3 + 18 ar(r2 - 1) = -18 ...(ii)
Dividing (ii) by (i), we get
Using r = -2 in (i), we get
a(4 - 1) = 9 a = 3
∴ Numbers are 3, 3(-2), 3(-2)2, 3(-2)3 or 3, -6, 12, -24