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What is the sum of the geometric sequence -4,24,-144, ... if there are 7 terms? A. -159,964 B.-26,661 C. 26,661 D. 159,964
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What is the sum of the geometric sequence -4,24,-144, ... if there are 7 terms?

A. -159,964
B.-26,661
C. 26,661
D. 159,964

User Lalit
by
8.9k points

1 Answer

4 votes

S_7=-4+24-144+864-5184+31104-186624

S_7=-4(1-6+36-216+1296-7776+46656)

(-6)S_7=-4(-6+36-216+1296-7776+46656-279936)

S_7-(-6)S_7=-4(1+279936)

S_7=-\frac47*279937=-159964
User Pranay Dutta
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8.8k points
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