\(=\left(1-\dfrac{\sqrt{5}\left(\sqrt{5}-1\right)}{\sqrt{5}-1}\right)\left(\dfrac{\sqrt{5}\left(\sqrt{5}+1\right)}{\sqrt{5}+1}+1\right)\)
=(1-căn 5)(1+căn 5)
=1-5
=-4
\(\left(1+\dfrac{5-\sqrt{5}}{1-\sqrt{5}}\right)\left(\dfrac{5+\sqrt{5}}{1+\sqrt{5}}+1\right)\)
\(=\left(1-\dfrac{\sqrt{5}\left(\sqrt{5}-1\right)}{\sqrt{5}-1}\right)\left(\dfrac{\sqrt{5}\left(\sqrt{5}+1\right)}{\sqrt{5}+1}+1\right)\)
\(=\left(1-\sqrt{5}\right)\left(\sqrt{5}+1\right)\)
\(=1^2-\left(\sqrt{5}\right)^2\)
\(=1-5\)
\(=-4\)
`(1+(5-\sqrt{5})/(1-\sqrt{5})).((5+\sqrt{5})/(1+\sqrt{5})+1)`
`=[1-(\sqrt{5}(\sqrt{5}-1))/(\sqrt{5}-1)].[(\sqrt{5}(\sqrt{5}+1))/(1+\sqrt{5})+1]`
`=(1-\sqrt{5})(1+\sqrt{5})`
`=1-5`
`=-4`
