Question

64, -48, 36, -27 which formula can be used to describe the sequence

Answer 1

 Formula      Multiply the number by  -3/4

The number 48 is 3/4 of 64 but it is negative so the result of -48 should be multiplying 64 by negative 3/4

64x-3/4 =-48

after 48 will be a positive number since (-)x(-)=(+)

So it will be alternating positive and negative

Answer 2

Answer is
f(x+1)=-3/4f(x)