Pamiętać należy :
[tex]\sqrt[n]{x} ~~gdy ~~x\geq 0\\\\szczegolny ~~przypadek:\\\\\sqrt{x^{2} }=(\sqrt{x} )^{2} =\mid x \mid\\\\(\sqrt{2-y} -y)\cdot (\sqrt{2-y} +y)=(\sqrt{2-y} )^{2} -y^{2} =\mid 2-y\mid -y^{2}\\\\\mid 2-y\mid -y^{2}~~\land ~~y=-\sqrt{2} ~~\Rightarrow ~~\mid2-(-\sqrt{2} )\mid-(-\sqrt{2} )^{2} =\mid2+\sqrt{2} \mid -2=2+\sqrt{2} -2=\sqrt{2} \\\\\\Odp:~~Wartosc~~wyrazenia~~wynosi~~\sqrt{2} ~~czyli~~poprawna~~odpowiedz~~to~~ B.[/tex]
