sum of an infinite geometric sequence with the common ratio r, and the first term a1 is \(\frac{a_1}{1-r}\)
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
\(\frac{-2}{1-(-0.25)}\)=
\(\frac{-2}{1+0.25}\)=
\(\frac{-2}{1.25}\)=
\(\frac{-8}{5}\)=
the sum is -8/5 or -1.6
