Question

Dada a PG (1, 3, 9, 27 e 81), determine a soma do a11 + a13

Answer 1

Resposta:

$\textsf{Leia abaixo}$

Explicação passo-a-passo:

$\mathsf{a_{n} = a_1.q^{n - 1}}$

$\mathsf{a_{11} = a_1.q^{11 - 1}}$

$\mathsf{a_{11} = 1.3^{10}}$

$\mathsf{a_{11} = 3^{10}}$

$\mathsf{a_{13} = a_1.q^{13 - 1}}$

$\mathsf{a_{13} = 1.3^{12}}$

$\mathsf{a_{13} = 3^{12}}$

$\mathsf{a_{11} + a_{13} = 3^{10} + 3^{12}}$

$\mathsf{a_{11} + a_{13} = 3^{10}( 1 + 3^{2})}$

$\boxed{\boxed{\mathsf{a_{11} + a_{13} = 10.3^{10} = 590.490}}}$