Find the first 5 terms of the geometric progression if the common ratio is -4 and the 4th term is 16.

Let a1, a2, a3, a4, a5 are terms of G.P such that r= -4 is
the common difference and a4 = 16

Then we know
that:

a4 = a1*r^3

==>
16 = a1* -4*3

==> 16 =
a1*-64

==> a1= -16/64 =
-1/4

==> a2= a1* r= -1/4 * -4=
1

==> a3= a1*r^2= -1/4* 16 =
-4

==> a4= a1*r^3 = -1/4* -64 =
16

==> a5= a1* r^4 = -1/4* 256 =
-64

==> Then the first 5 terms
are:

-1/4....1.....-4......16......-64