agree or disagree and prove : UA = UB then A=B agree or disagree and prove : union of A equal union of B then A equal to B .

Union of $\\{1,2\\}$ and $\\{3,4\\}$ is the same as union of $\\{1,3\\}$ and $\\{2,4\\}$

But collections A={ {1,2} , $\\{3,4\\}\\}$ and $B= \\{\\{1,3\\} , \\{2,4\\}\\}$ are not the same.