anonymous one year ago What is the sum of the geometric sequence 8, -16, 32 . if there are 15 terms?

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1. anonymous

a=8 r=-16/8=-2 n=15 $S _{n}=\frac{ a \left( r^n-1 \right) }{ r-1 }$

2. anonymous

Thanks so much~

3. anonymous

yw