Question

Determine a soma dos 8 primeiros termos das seguintes P.G.
A)(3,12,48...)
B)(-4,8,-16...)
C)(5000,500,50...)​

Answer 1

Sn=a1(q^n-1)/q-1 (finita)

a) a1=3 q=4

3(4^8-1)/3

3(65536-1)/3

3×65535/3

65535

b) a1=-4 q=-2

-4((-2)^8-1)/-2-1

-4(256-1)/-3

-4×255/-3

-4×85/-1

340

c) a1=5×10^3 q=10^-1

5×10^3((10^-1)^8-1)/0,1-1

5×10^3(10^-8 -1)/-0,9

5×10^-5 - 5×10^3/-0,9

-4999,99995/-0,9

5555,5555