Question

Задание 2, под номером 17) помогите

Answer 1

=3*(-1)*(-6)+(-5)*5*4+(-4)*1*(-3)-((-4)*(-1)*4+3*5*(-3)+(-5)*1*(-6))=18-100+12-(16-45+30)=30-100-16+45-30=75-146-71

Answer 2

$A=left(begin{array}{ccc}3&-5&-4\1&-1&5\4&-3&-6end{array}right) \\\detA=3cdot (6+15)+5(-6-20)-4(-3+4)=-71ne 0\\A_{11}=21; ,; ; A_{12}=26; ,; ; A_{13}=1\\A_{21}=-18; ,; ; A_{22}=-2; ,; ; A_{23}=-11\\A_{31}=-29; ,; ; A_{32}=-19; ,; ; A_{33}=2\\\A^{-1}=-frac{1}{71}cdot left(begin{array}{ccc}21&-18&-29\26&-2&-19\1&-11&2end{array}right)$


$A^{-1}cdot A=-frac{1}{71}cdot left(begin{array}{ccc}21&-18&-29\26&-2&-19\1&-11&2end{array}right)cdot left(begin{array}{ccc}3&-5&-4\1&-1&5\4&-3&-6end{array}right)=$

$=-frac{1}{71}cdot left(begin{array}{ccc}-71&0&0\0&-71&0\0&0&-71end{array}right) = left(begin{array}{ccc}1&0&0\0&1&0\0&0&1end{array}right)$