Question

sa se calculeze inversa matricelor :
A(1  7
   2 -1)

Answer 1

$\left[\begin{array}{ccc}1&7\\2&-1\\\end{array}\right] \\ A^{-1}= \frac{1}{det(A)} * A^{*-stelat} \\ det(A)=-15 rezulta det(A) \neq 0   rezulta exista { A^{-1} } \\ A^{*} = \left[\begin{array}{ccc}-1&-2&\\-7&1&\\\end{array}\right] \\ A^{-1} = \frac{1}{-15} * \left[\begin{array}{ccc}-1&-2&\\-7&1&\\\end{array}\right] \\ A^{-1} = \left[\begin{array}{ccc} \frac{1}{15} & \frac{2}{15} \\ \frac{7}{15} & \frac{1}{-15} \\\end{array}\right]$