Question 991823
The inverse of a 2x2 matrix,
{{{A=(matrix(2,2,a,b,c,d))}}} is equal to the determinant, 
{{{D=1/(ad-bc)}}} multiplied by the matrix
{{{M=(matrix(2,2,d,-b,-c,a))}}}
Just substitute the values.
{{{A^(-1)=D*M}}}