Question 626892
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Hi,
A={{{(matrix(3,3,a1,b1,c1,a2,b2,c2,a3,b3,c3))}}} ={{{(matrix(3,3,2,-1,0,2,1,0,0,0,1))}}}
I. find value of determinant =  a1(b2c3-c2b3) - b1(a2c3-c2a3) + c1(a2b3-b2a3) = {{{4}}}
II. Then Apply formula for the Inverse:
{{{A^(-1)}}} = {{{ 1/d}}}{{{matrix(3,3,(b2*c3-c2*b3),(c1*b3-b1*c3),(b1*c2-c1*b2),
                   (c2a3-a2c3),(a1c3-c1a3),(c1a2-a1c2),
                   (a2b3 - b2a3), (b1a3 -a1b3),(a1b2-b1a2)))}}}

{{{A^(-1)}}}  = {{{1/4}}}{{{(matrix(3,3,1,1,0,-2,2,0,0,0,4))}}}