Write 6 terms the geaometric progression such that the common difference is -3 and the 3rd term is 18.

Let us review the rules for the geometric
progression.

Let a1, a2, a3, a4, a5, a6 are the first 6
terms is a G.P.

Let r be the common
difference.

Then, we know
that>

a1= a1

a2=
a1*r

a3= a1*r^2

a4=
a1*r^3

a5= a1*r^4

a6=
a1*r^5

Given that r= -3 and a3 =
18

==> a3=
a1*r^2

==> 18 =
a1*-3^2

==> 18 =
a1*9

==> a1= 18/9 =
2

==> a2= a1*r = 2*-3 =
-6

==> a3=
18

==> a4= a1*r^3= 2*-3^3 = 2*-27 =
-54

==> a5= 2*-3^4 = 2*81 =
162

==> a6= 2*-3^5 =
-486

Then the first six terms
are;

2, -6, 18, -54, 162,
-486.