Question 1187380
3 terms apart have a ratio of -8 in a geometric progression so r=-2. If second term is -6, first term is 3.
sum is a(1-r^n)/(1-r)
S= 3((1-(-2)^4)/(1-(-2))
=-45/3
=-15
the terms are 3, -6, 12, -24, 48
That is the first five terms, and the sum of the first four is -15