Answer:
615
Explanation:
The ratio of the given terms can be used to find the common ratio between terms:
a5/a2 = (a1·r^(5-1))/(a1·r^(2-1)) = r^3 = 768/-12 = -64
r = ∛-64 = -4
So the first term is ...
a1 = a2/r = -12/-4 = 3
And the first 5 terms of the series are ...
3 + (-12) + (48) + (-192) + 768 + ...
The sum of the first 5 terms is 615.