Question

Dada a PG ( 5, 10, 20, 40, 80...) calcule a soma dos sete primeiro termos desta PG A) 356 B) 536 C) 635 D) 565

Answer 1

Soma dos termos de uma PG finita

$\large\boxed{\boxed{\boxed{\boxed{\mathsf{S_{n}=\dfrac{a_{1}(q^n-1)}{q-1}~q\ne1}}}}}$

$\boxed{\boxed{\boxed{\boxed{\mathsf{S_{7}=\dfrac{5(2^7-1)}{2-1}=5.(128-1)=5.127}}}}}\\\boxed{\boxed{\boxed{\boxed{\mathsf{S_{7}=635}}}}}$