What is the sum of the first seven terms of the geometric series 3 − 6 + 12 − . . . ? Hint: cap s sub n equals start fraction a sub one left parenthesis one minus r to the power of n end power right parenthesis over one minus r end fraction comma r ≠ 1, where a1 is the first term and r is the common ratio. (4 points)

S7 = −63
S7 = −9
S7 = 33
S7 = 129