contestada

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

Respuesta :

LammettHash
[tex]S_7=-4+24-144+864-5184+31104-186624[/tex]
[tex]S_7=-4(1-6+36-216+1296-7776+46656)[/tex]
[tex](-6)S_7=-4(-6+36-216+1296-7776+46656-279936)[/tex]
[tex]S_7-(-6)S_7=-4(1+279936)[/tex]
[tex]S_7=-\dfrac47\times279937=-159964[/tex]

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