Question

A soma dos nove primeiros termos da PG ( 2, -4, 8 )

Answer 1

q = a2/a1 = —4/2 = —2

a1 = 2

n = 9

Sn=S9=??

Logo:

Sn=[a1.(q^n-1)]/q-1

S9=[2.(-2^9-1)]/-2-1

S9=[2.(-512-1)]/-3

S9=(2.-513)/-3

S9=-1026/-3

S9=342