`E=x/(\sqrt{x^2-y^2})-((\sqrt{x^2-y^2}+x)/(\sqrt{x^2-y^2}):y/(x-\sqrt{x^2-y^2}))`
(Đk: `x>y`)
`E=x/(\sqrt{x^2-y^2})-((x+\sqrt{x^2-y^2})(x-\sqrt{x^2-y^2}))/(y\sqrt{x^2-y^2})`
`E=x/(\sqrt{x^2-y^2})-(x^2-\sqrt{(x^2-y^2)^2})/(y\sqrt{x^2-y^2})`
`E=x/(\sqrt{x^2-y^2})-(x^2-|x^2-y^2|)/(y\sqrt{x^2-y^2}`
`E=x/(\sqrt{x^2-y^2})-(x^2-x^2+y^2)/(y\sqrt{x^2-y^2}`
`E=(x-y)/(\sqrt{x^2-y^2})`