Question 632917
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Hi,
Note: Post each question separately, not necessary to use pictures,
just list Eqs with the following instructions:
Solve the system of equations by using the inverse of the coefficient matrix.
 x+3y = -9 
5x+8y = -31                             
{{{A =( matrix(2,2,1,3,5,8))}}} = -7  
{{{adjA = (matrix(2,2,8,-3,-5,1))}}}  Note: How the above numbers flipped and the 2 minuses
{{{A^(-1)}}} = (1/-7){{{ (matrix(2,2,8,-3,-5,1)) }}}

{{{A^(-1) =  (matrix(2,2,-8/7,3/7,5/7,-1/7)) }}}
and...
{{{(matrix(2,1,x,y))= (matrix(2,2,-8/7,3/7,5/7,-1/7)) (matrix(2,1,-9,-31))= (matrix(2,1,-3,-2)) }}}
Ordered pair (-3,-2) the solution for this system of equations
Checking our answer using the Elimination Method:
x+3y= -9 
5x+8y= -31  |multiplying 1st EQ by 5 and Subtracting  from the 2nd EQ
 -7y = 14
  y = -2   and x = -3  as {{{-3 + 3*(-2) = -9}}}
(x,y) Ordered pair (-3,-2) the solution for this system of equations