the question does not present the options, but this
does not interfere with the resolution
Let
a1=-4
a2=-24
a3=-144
a4=-864
a5=?
we know that
a2/a1=-24/-4----> 6-------> a2=6*a1
a3/a2=-144/-24---> 6-----> a3=6*a2
a4/a3=-864/-144---> 6----> a4=6*a3
therefore
a5=6*a4-----> a5=6*(-864)------> a5=-5184
hence
the formula is
an=6*a(n-1)
n and (n-1) are subscripts
