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AB+BC+CA:11  VA ROOG!!!




Răspuns :

AB+BC+CA=10A+B+10B+C+10C+A=11A+11B+11C=11(A+B+C)

⇒AB+BC+CA:11=A+B+C


AB+BC+CA:11=
(10A+B+10B+C+10C+A):11=
(11A+11B+11C):11=
11(A+B+C):11=A+B+C