resoudre par combinaison le systeme: {-4x+2y=-1 { 8x-5y=7

[tex] \left[\begin{array}{cc}x&y\end{array}\right] \left[\begin{array}{cc}-4&2\\8&-5\\\end{array}\right] = \left[\begin{array}{cc}-1&7\end{array}\right] = XA=B[/tex]

On cherche donc à résoudre X = B [tex]A^{-1}[/tex]

[tex]\left[\begin{array}{cc}-4&2\\8&-5\\\end{array}\right]^{-1} = \frac{1}{(-4)(-5)-8*2}\left[\begin{array}{cc}5&8\\2&4\\\end{array}\right] = \frac{1}{4}\left[\begin{array}{cc}5&8\\2&4\\\end{array}\right][/tex]

X == [tex]\frac{1}{4}\left[\begin{array}{cc}-1&7\\\end{array}\right]\left[\begin{array}{cc}5&8\\2&4\\\end{array}\right][/tex]