Question

Fie suma S=3³+3⁴+3⁵+3⁶+3⁷+3⁸+......+3²⁰¹⁸. S=?​

Answer 1

Răspuns:

Explicație pas cu pas:

avem o progresie geometrica de ratie q = 3 si

2018-3 + 1 = 2016 termeni.

S = 3^3 (3^2016 - 1) / 3-1 =

27(3^2016 - 1) / 2 =

13,5(3^2016 - 1).

Answer 2

$\it S=3^3(1+2+3^2+\ ...\ +3^{2015})=3^3\cdot\dfrac{3^{2016}-1}{3-1}=\dfrac{27}{2}(3^{2016}-1)$