Question

b1=4 q=-3 S4-? ПАМАГИТЕЕЕЕЕЕЕЕЕЕ

Answer 1

b1=4 q=-3 

$S_{n}=frac{b_{1}(q^{n}-1)}{q-1}$

$S_{4}=frac{4((-3)^{4}-1)}{-3-1}=frac{4(81-1)}{-4}=-80$

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