Răspuns:
AE/AB= 1/4
AF/FC=1/3
GD/AD=3/4
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(EFG) // (BCD)
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AF/FC= 1/3=k=> AF= k, FC=3k
AF/AC= k/k+3k= k/4k= 1/4
GD/AD=3/4= k=> GD= 3k, AD= 4k
AG/AD= 4k-3k/4k= k/4k= 1/4
ΔABD
AE/AB=AF/FC=1/4=> EF//BC
ΔACD
AF/AC=AG/AD=1/4=> FG//CD
EF//BC
FG//CD
EF, FG⊂(EFG)
EF∩FG= {F}
BC, CD⊂(BCD)
BC∩CD= {C}
=> (EFG)//(BCD)