Question

Calcule a soma dos 7 primeiros termos da P.G (5,15,45.....)

Answer 1

vamos achar a razão

q = 15/5
q = 3

S7 = a1(qⁿ - 1) / q -1

S7 = 5.(3^7 - 1) / 2

S7 = 5.(2187 - 1) / 2

S7 = 5.2186/2

S7 = 5465 ← Resposta.


att: Jhonny

Answer 2

a₁ = 5
q = 15/3 
q = 5

$Sn = \frac{ a_{1( q^{n} -1)} }{q-1} \\ \\ S7= \frac{5( 3^{7}-1) }{3-1} \\ \\ S7= \frac{5(2187-1)}{2} \\ \\ S7= \frac{10930}{2} \\ \\ S7=5465$