A + B = [tex] \left(\begin{array}{ccc}1&1\\-1&0\end{array}\right)+ \left(\begin{array}{ccc}0&-1\\1&1\end{array}\right)=\left(\begin{array}{ccc}1&0\\0&1\end{array}\right)= I_2 [/tex]
A + B = [tex] \left(\begin{array}{ccc} 2^{x} &0\\0&4^x\end{array}\right) =\ \textgreater \ \left(\begin{array}{ccc} 2^{x} &0\\0&4^x\end{array}\right) =\left(\begin{array}{ccc} 1 &0\\0&1\end{array}\right)=\ \textgreater \ \left \{ {{2^x=1} \atop {4^y=1}} \right. =\ \textgreater \ x= 0[/tex] si y= 0
