$A=(1-\frac{1}{x^2})(1-\frac{1}{y^2})=1-\frac{1}{x^2}-\frac{1}{y^2}+\frac{1}{x^2y^2}=1-\frac{x^2+y^2}{x^2y^2}+\frac{1}{x^2y^2}=1-\frac{(x+y)^2-2xy}{x^2y^2}+\frac{1}{x^2y^2}=1+\frac{2}{xy}$mà $xy\leq \frac{(x+y)^2}{4}=\frac{1}{4}\Rightarrow A\geq 1+8=9$