Question

Calcule a soma dos oito primeiros termos da pg (-5, 10, -20...)

Answer 1

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

Sn= -5 x -2^8-1 / -2 - 1

Sn= -5 x -128 / -3

Sn= 640/ -3

Sn= -213,3