Which formula can be used to describe the sequence?

Negative 3, three-fifths, negative StartFraction 3 Over 25 EndFraction, StartFraction 3 Over 125 EndFraction, negative StartFraction 3 Over 625 EndFraction

f(x) = −3(One-fifth) Superscript x minus 1
f(x) = −3(Negative one-fifth) Superscript x minus 1
f(x) = Negative one-fifth(3)x − 1
f(x) = Negative one-fifth(−3)x − 1