Question

ME AJUDEM É PRA AMANHÃ!!!! Quanto dá a soma dos 4 primeiros termos da P.G. (4,12,36....)?

Answer 1

Soma dos termos de uma PG finita

$\huge\boxed{\boxed{\boxed{\boxed{\mathsf{S_{n}=\dfrac{a_{1}\cdot(1-q^n)}{1-q}}}}}}$

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$\mathsf{a_{1}=4~~~q=\dfrac{12}{4}=3~~~n=4}\\\mathsf{S_{n}=\dfrac{a_{1}\cdot(1-q^n)}{1-q}}\\\mathsf{S_{4}=\dfrac{4\cdot(1-3^4)}{1-3}}\\\mathsf{S_{4}=\dfrac{4(1-81)}{-2}}\\\mathsf{S_{4}=-2\cdot(-80)}\\\huge\boxed{\boxed{\boxed{\boxed{\mathsf{S_{4}=160}}}}}$

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