Answer:
This is a geometry sequence (I.e each term is found by multiplying the same value to the previous term).
T1 = 4
T2 = -12 = T1 X (-3) = 4 X (-3)
T3 = 36 = T2 X (-3) = 4 X (-3)^2
T4 = 108 = T3 X (-3) = 4 X (-3)^3
The general (explicit) formula for the n-th term of this sequence is:
S(n) = 4 X (-3)^(n-1)
