Question

x2-{[x-2y+x2-(x-2y)]-y}

Answer 1

$x^2-([x-2y+x^2-(x-2y)]-y) \\ \\ x^{2} -([x-2y+ x^{2} -x+2y]-y) \\ \\ x^{2} -( x^{2} -y) \\ \\ x^{2} - x^{2} +y \\ \\ y$