Răspuns:
Explicație pas cu pas:
b1 + b2 = b1 + b1*q = b1*(1 + q)
b2 + b3 = b1*q + b1*q^2 = b1*q*(1 + q)
b1*(1 + q)/b1*q*(1 + q) = 1/3
1/q = 1/3
q = 3
b1 + b2 + b3 = 52
b1 + b1*q + b1*q^2 = 52
b1 + 3b1 + 9b1 = 52
13b1 = 52
b1 = 52 : 13 = 4
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b1 = 4
b2 = 4*3 = 12
b3 = 12*3 = 36
b4 = 36*3 = 108
b5 = 108*3 = 324
S5 = 4 + 12 + 36 + 108 + 324 = 484
