If $x^{4} + x^{2} y^{2} + y^{4} = 273$ and $x^{2} - xy + y^{2} = 13$, then the value of xy is :

4 10 6 8

4

x4 + x2y2 + y4 = (x2 – xy + y2) (x2 + xy + y2) If $x^{4} + x^{2} y^{2} + y^{4} = 273$ $x^{2} - xy + y^{2} = 13$ ----(A) Then, $x^{2} + xy + y^{2} = \frac{273}{13}$ = 21-----(B) From equation A and B The value of xy = 4