`(\sqrt{x+3}-\sqrt{x+1})(x^2+\sqrt{x^2+4x+3})=2x` `ĐKXĐ: x≥-1`
`⇔x^2+\sqrt{x^2+4x+3}=2x/(\sqrt{x+3}-\sqrt{x+1})` `(\sqrt{x+3}-\sqrt{x+1}≠0∀x≥-1)`
`⇔x^2+\sqrt{(x+3)(x+1)}=(2x(\sqrt{x+3}+\sqrt{x+1}))/2` `(\sqrt{x+3}+\sqrt{x+1}≠0∀x≥-1)`
`⇔x^2+\sqrt{(x+3)(x+1)}-x \sqrt{x+3}-x \sqrt{x+1}=0`
`⇔(x-\sqrt{x+3})(x-\sqrt{x+1}=0`
`⇔x=(1+\sqrt{13})/2` hoặc `x=(1+\sqrt{5})/2`
