`1, (\sqrt{x}-\sqrt{y})^2`
`= x-2\sqrt{xy}+y`
`2, (\sqrt{x}+1)(\sqrt{x}-1)`
`=x-1`
`3, 25x-4y`
Với `x>=0; y>=0` thì:
`25x-4y=(5\sqrt{x})^2-(2\sqrt{y})^2=(5\sqrt{x}-2\sqrt{y})(5\sqrt{x}+2\sqrt{y})`
Với `x>=0;y<0` thì
`25x-4y=(5\sqrt{x})^2-(2\sqrt{-y})^2=(5\sqrt{x}-2\sqrt{-y})(5\sqrt{x}+2\sqrt{-y})`
Với `x<0;y>=0` thì:
`25x-4y=(5\sqrt{-x})^2-(2\sqrt{y})^2=(5\sqrt{-x}+2\sqrt{y})(5\sqrt{-x}+\sqrt{y})`
Với `x<0;y<0` thì
`25x-4y=(5\sqrt{-x})^2-(2\sqrt{-y})^2=(5\sqrt{-x}-2\sqrt{-y)(5\sqrt{-x}+2\sqrt{-y})`
`4, (\sqrt{x})^3-1`
`=(\sqrt{x}-1)(x+\sqrt{x}+1)`
`5, (\sqrt{x})^3+1`
`=(\sqrt{x}+1)(x-\sqrt{x}+1)`
