The perfect square
Let's highlight the perfect square of the square three-member
$$- 8 x^{2} + \left(- x 8 y - y^{2}\right)$$
Let us write down the identical expression
$$- 8 x^{2} + \left(- x 8 y - y^{2}\right) = y^{2} + \left(- 8 x^{2} - 8 x y - 2 y^{2}\right)$$
or
$$- 8 x^{2} + \left(- x 8 y - y^{2}\right) = y^{2} - \left(2 \sqrt{2} x + \sqrt{2} y\right)^{2}$$
General simplification
[src]
$$- 8 x^{2} - 8 x y - y^{2}$$
/ / ___\\ / / ___\\
| y*\-2 + \/ 2 /| | y*\2 + \/ 2 /|
|x - --------------|*|x + -------------|
\ 4 / \ 4 /
$$\left(x - \frac{y \left(-2 + \sqrt{2}\right)}{4}\right) \left(x + \frac{y \left(\sqrt{2} + 2\right)}{4}\right)$$
(x - y*(-2 + sqrt(2))/4)*(x + y*(2 + sqrt(2))/4)
$$- 8 x^{2} - 8 x y - y^{2}$$
Combining rational expressions
[src]
$$- 8 x^{2} + y \left(- 8 x - y\right)$$
$$- 8 x^{2} - 8 x y - y^{2}$$
Rational denominator
[src]
$$- 8 x^{2} - 8 x y - y^{2}$$
$$- 8 x^{2} - 8 x y - y^{2}$$
$$- 8 x^{2} - 8 x y - y^{2}$$
Assemble expression
[src]
$$- 8 x^{2} - 8 x y - y^{2}$$