The perfect square
Let's highlight the perfect square of the square three-member
$$15 x^{2} + \left(- x y - y^{2}\right)$$
Let us write down the identical expression
$$15 x^{2} + \left(- x y - y^{2}\right) = - \frac{61 y^{2}}{60} + \left(15 x^{2} - x y + \frac{y^{2}}{60}\right)$$
or
$$15 x^{2} + \left(- x y - y^{2}\right) = - \frac{61 y^{2}}{60} + \left(\sqrt{15} x - \frac{\sqrt{15} y}{30}\right)^{2}$$
in the view of the product
$$\left(- \sqrt{\frac{61}{60}} y + \left(\sqrt{15} x + - \frac{\sqrt{15}}{30} y\right)\right) \left(\sqrt{\frac{61}{60}} y + \left(\sqrt{15} x + - \frac{\sqrt{15}}{30} y\right)\right)$$
$$\left(- \frac{\sqrt{915}}{30} y + \left(\sqrt{15} x + - \frac{\sqrt{15}}{30} y\right)\right) \left(\frac{\sqrt{915}}{30} y + \left(\sqrt{15} x + - \frac{\sqrt{15}}{30} y\right)\right)$$
$$\left(\sqrt{15} x + y \left(- \frac{\sqrt{15}}{30} + \frac{\sqrt{915}}{30}\right)\right) \left(\sqrt{15} x + y \left(- \frac{\sqrt{915}}{30} - \frac{\sqrt{15}}{30}\right)\right)$$
$$\left(\sqrt{15} x + y \left(- \frac{\sqrt{15}}{30} + \frac{\sqrt{915}}{30}\right)\right) \left(\sqrt{15} x + y \left(- \frac{\sqrt{915}}{30} - \frac{\sqrt{15}}{30}\right)\right)$$
General simplification
[src]
$$15 x^{2} - x y - y^{2}$$
/ / ____\\ / / ____\\
| y*\1 - \/ 61 /| | y*\1 + \/ 61 /|
|x - --------------|*|x - --------------|
\ 30 / \ 30 /
$$\left(x - \frac{y \left(1 - \sqrt{61}\right)}{30}\right) \left(x - \frac{y \left(1 + \sqrt{61}\right)}{30}\right)$$
(x - y*(1 - sqrt(61))/30)*(x - y*(1 + sqrt(61))/30)
Combining rational expressions
[src]
$$15 x^{2} + y \left(- x - y\right)$$
$$15 x^{2} - x y - y^{2}$$
Assemble expression
[src]
$$15 x^{2} - x y - y^{2}$$
$$15 x^{2} - x y - y^{2}$$
$$15 x^{2} - x y - y^{2}$$
$$15 x^{2} - x y - y^{2}$$
Rational denominator
[src]
$$15 x^{2} - x y - y^{2}$$