Question 481071
x = {{{abs(matrix(2,2,a^2 + b^2, -b, 2b^2 + 3ab - a^2, -a))/abs(matrix(2,2,a, -b, 2b, -a))}}}
=  {{{(-a^3 + 2ab^2 - a^2b + 2b^3)/(-(a^2 - 2b^2))}}}
= {{{(-(a+b)(a^2 - 2b^2))/(-(a^2 - 2b^2))}}}
= a+b
==> y = a - b, after substitution into the first equation.