Đáp án:
Giải thích các bước giải:
Câu `9`
`b)`
`VT=(x\sqrty+y\sqrt{x})/sqrt{xy}:1/(\sqrt{x}-\sqrt{y}`
`ĐK:x,y>0,x \ne y`
`=(\sqrt{xy}(\sqrt{x}+\sqrt{y}))/sqrt{xy}:1/(\sqrt{x}-\sqrt{y}`
`=(\sqrt{x}+\sqrt{y}):1/(\sqrt{x}-\sqrt{y}`
`=(\sqrt{x}+\sqrt{y})(\sqrt{x}-\sqrt{y})`
`=x-y=VP`
`=>đpcm`
`c)`
`VT=\sqrt{y}/(x-\sqrt{xy})+\sqrt{x}/(y-\sqrt{xy})`
`ĐK:x,y>0,x \ne y`
`=\sqrt{y}/(x-\sqrt{xy})-\sqrt{x}/(\sqrt{xy}-y)`
`=\sqrt{y}/(\sqrt{x}(\sqrt{x}-\sqrt{y}))-\sqrt{x}/(\sqrt{y}(\sqrt{x}-\sqrt{y})`
`=y/(\sqrt{xy}(\sqrt{x}-\sqrt{y}))-x/(\sqrt{xy}(\sqrt{x}-\sqrt{y})`
`=(y-x)/(\sqrt{xy}(\sqrt{x}-\sqrt{y}))`
`=(-(\sqrt{x}-\sqrt{y})(\sqrt{x}+\sqrt{y}))/(\sqrt{xy}(\sqrt{x}-\sqrt{y}))`
`=-(\sqrt{x}+\sqrt{y})/(\sqrt{xy})=VP`
`=>đpcm`
