Question

Salut! Va rog calculați :
2×(1+3+3^2+...+3^49)

Answer 1

   
[tex]\displaystyle \\ 2\times (1+3+3^2+\cdots+3^{49}) = 2\times \frac{3^{49+1} -1}{3-1} =2\times \frac{3^{50} -1}{2} = \boxed{3^{50} -1}[/tex]

Answer 2

1+3+3^2+...+3^49=(3^50-1)/2

2* (3^50-1)/2 = 3^50-1