Question

encontre a soma dos termos da p.g (3/4,-1/2,1/3,-1/9).

Answer 1

1) calculamos a razão
razão = a2/a1 = (-1/2) / (3/4) = (-1/2 * 4/3) = - 4/6 = -2/3

3) calculamos a soma até o 4º termo:

Sn = [a1*(r^n - 1)] / r - 1 
S4 = [3/4 * (-2/3^4 - 1)] / 3/4-1
S4 = [ 3/4 * (-16/81 - 1)] / -1/4
S4 = [3/4 * -97/81 ] / 1/4
S4 = -291/324 / 1/4
S4 = -1164/324
S4= -582/162
S4= -291/81
S4=-97/27
 
abs.