The sum of the infinite G.P. a + a r2 + a r3 . . . . . . a is finite. Then,
r > 1
r < 0
r > 0
-1 < r < 1
For the sum to exist, arn should approach zero as n becomes infinity. This is possible when |r|<1
If the sides fo a triangle are in A.P. as well as in G.P. Then the value of r1r2−r2r3