รบกวนอีกสองข้อครับ
Find all ordered pairs (x, y) of positive integers which satisfy the equation $x^{3}+y^{3}=x^{2}+18xy+y^{2}$.
The quadrilateral ABCD is inscribed in a circle with center O. Connect AC and BD intersecting at K. $O_{1}$ is the circumcenter of triangle ABK and $O_{2}$ is the circumcenter of triangle CDK. A line l through K intersect the two circumcircles at E and F respectively, and the circumcircle of ABCD at G and point H. Prove that EG = FH.
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