อ้างอิง:
ข้อความเดิมเขียนโดยคุณ Mastermander
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$ x^2+y^2-4xy = (x^2+2xy+y^2)-6xy = (x+y+\sqrt{6xy})\cdot (x+y-\sqrt{6xy}) $
$-2x^2+2x+7 = (-2)\cdot (x^2-x-\frac{7}{2}) = (-2)\cdot (x^2-2(\frac{1}{2})x+\frac{1}{4}-\frac{1}{4}-\frac{7}{2})$
$-2x^2+2x+7 = (-2)\cdot ((x-\frac{1}{2})^2-\frac{15}{4}) = (-2)\cdot (x-\frac{1+\sqrt{15}}{2})(x-\frac{1-\sqrt{15}}{2})$
$x^6-y^6 = (x^3)^2-(y^3)^2 = (x^3+y^3)(x^3-y^3)=(x+y)(x-y)(x^2+xy+y^2)(x^2-xy+y^2)$