Sum of an infinite geometric sequence with the common ratio r, and the first term a1 is 
we notice
-2 times -1/4=1/2,
1/2 times -1/4=-1/8
so a1=-2
r=-1/4 or -0.25
so the sum is
=
=
=
=
the sum is -8/5 or -1.6
we notice
-2 times -1/4=1/2,
1/2 times -1/4=-1/8
so a1=-2
r=-1/4 or -0.25
so the sum is
the sum is -8/5 or -1.6