Răspuns:
A___________B
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D___________C
AB-AD=3 =>AB=AD+3
AC=AD+6
AD^2 + (AD+3)^2 = (AD+6)^2 (t.Pitagora)
AD^2 + AD^2 + 6AD + 9 = AD^2 + 12AD + 36
AD^2 + 6AD + 9 - 12AD - 36 = 0
AD^2 - 6AD - 27 = 0
delta = 36+4•27 = 36+108 = 144 =>rad.delta = 12
AD=(6+12)/2=9 cm
AC=15 cm