*Demonstrati egalitatea : [tex]\left[\begin{array}{ccc}2&4\\1&3&\\\end{array}\right][/tex]-3[tex]\left[\begin{array}{ccc}5&2\\2&1&\\\end{array}\right][/tex]=[tex]\left[\begin{array}{ccc}0&1&\\1&0&\\\end{array}\right][/tex]

*Fie matricele A=[tex]\left(\begin{array}{ccc}3&-2&\\4&-1&\\\end{array}\right)[/tex] si B=3A.
Demonstrati ca det(B)=9det(A).