Răspuns:
0,1(9) = (19-1)/90 = 18/90 = 2/10 = 0,2 # 0,1(9)
b = 1/2 × 2/9 - 10/3 × (18/90 - 21/99 × 13/16) =
b = 1/9 - 10/3 × (1/5 - 7/33 × 13/16) =
b = 1/9 - 10/3 × (1/5 - 91/528)
b = 1/9 - 10/3 × (528 - 455)/2640
b = 1/9 - 10/3 × 73/2640
b = 1/9 - 73/792
b = (264 - 73)/792
b = 191/792
b = 0,241(161)
c = (4rad3 - 6rad3 + 6rad3 - 2rad3 + 2rad3) × rad3
c = 4rad3
