X^2-y^2=3, x^4-y^4=15 решить систему

[latex] \left\{{{x^{2} -y^{2} =3}\atop { x^{4} -y^{4} =15}} \right. [/latex] [latex] x^{2} =3+ y^{2} [/latex] [latex](3+ y^{2})^{2}- y^{4}=15[/latex] [latex]9+y^{2}+ y^{4} - y^{4} =15[/latex] [latex] 6y^{2} =6[/latex] [latex] y^{2}=+/- 1 [/latex] [latex]y=+/-1[/latex] [latex] x^{2} =3+/- 1^{2} =4[/latex] [latex]x = +/-2[/latex]