(Q25).Which of the following are G.P. ? If they are G.P, write three more terms,

(iv) -2, -6, -18, ……

Given: t1 = -, t2 = -, t3 = -

t2
t1
 =
-
-
 = ;
t3
t2
 =
-
-
 =
∴ r =
t2
t1
 =
t3
t2
 = ......... =

∴ -2, -6, -18, is a G.P.

where a = - and r =

an = a . rn-1

a4 = a . r3 = (-) × 3 = - × = -

a5 = a . r4 = (-) × 4 = - × = -

a6 = a . r5 = (-) × 5 = - × = -