Sn = [a1·(q^n - 1)]/(q-1) или Sn = [a1·(1-g^n)]/(1-q) ⇒
b). S10 = (-1/36) ·[1-(-2)^10]/[1-(-2)] = - 1/36 ·(-1023) /3 = 1023/108
c) S6 = (-1/27) ·(3^6 - 1)/(3-1) = -1/27 ·728/2 = - 364/27 = -13'13/27
d) S^ = -2/27 ·[1-(-3)^6]/[1-(-3)] = -2/27 ·(-728)/4 = 364/27 = 13'13'27