\(A=\left(\frac{1}{x^2+2xy+y^2}-\frac{1}{x^2-y^2}\right):\frac{4xy}{y^2-x^2}\)ĐK : \(x\ne y;x\ne-y;x;y\ne0\)
\(=\left(\frac{x-y}{\left(x-y\right)\left(x+y\right)^2}-\frac{x+y}{\left(x-y\right)\left(x+y\right)^2}\right):\frac{4xy}{y^2-x^2}\)
\(=\frac{2y}{\left(x-y\right)\left(x+y\right)^2}.\frac{\left(x-y\right)\left(x+y\right)}{4xy}=\frac{1}{2x\left(x+1\right)}\)