Question

calcule a soma dos sete primeiros termos da PG (2,4,8...)

Answer 1

$PG (2,4,8...) \\\\S_{n} = S_{7} =?\\ a_{1} =2\\q=2\\n=7\\\\\\ S_{n} = \frac{a_{1} (q^n-1)}{q-1} \\\\\\S_{7} = \frac{2(2^7-1)}{2-1} \to\\\\ S_{7} = \frac{2(128-1)}{1} \to\\\\ S_{7} = \frac{2*127}{1} \to\\\\S_{7} =254$