exo7 3399

Soient $A = \begin{pmatrix} 1 &\frac12 &\frac13 \cr \frac12 &\frac13 &\frac14 \cr \frac13 &\frac14 &\frac15 \cr \end{pmatrix}$ et $B = \begin{pmatrix} 1\phantom{.00} &0.5\phantom{0} &0.33 \cr 0.5\phantom{0} &0.33 &0.25 \cr 0.33 &0.25 &0.20 \cr \end{pmatrix}$. Calculer $A^{-1}$ et $B^{-1}$.