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Étudier l’existence de solutions du système : \[\left\{\begin{array}{ccccccc} 3mx &+& (3m-7)y &+& (m-5)z &=& m-1 \cr (2m-1)x &+& (4m-1)y &+& 2mz &=& m+1 \cr 4mx &+& (5m-7)y &+& (2m-5)z &=& 0. \cr\end{array}\right.\]
Étudier l’existence de solutions du système : \[\left\{\begin{array}{ccccccc} 3mx &+& (3m-7)y &+& (m-5)z &=& m-1 \cr (2m-1)x &+& (4m-1)y &+& 2mz &=& m+1 \cr 4mx &+& (5m-7)y &+& (2m-5)z &=& 0. \cr\end{array}\right.\]