Подстановка условия
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x^7 + x - y^7 - y при y = -1/3
$$x^{7} - y^{7} + x - y$$
$$x^{7} - y^{7} + x - y$$
$$y = - \frac{1}{3}$$
7 7
x + x - (-1/3) - (-1/3)
$$- (-1/3)^{7} + x^{7} - (-1/3) + x$$
$$x^{7} + x - \left(- \frac{1}{3}\right)^{7} - - \frac{1}{3}$$
$$x^{7} + x + \frac{730}{2187}$$
/ 6 6 5 5 2 4 3 3 4 2\
(x - y)*\1 + x + y + x*y + y*x + x *y + x *y + x *y /
$$\left(x - y\right) \left(x^{6} + x^{5} y + x^{4} y^{2} + x^{3} y^{3} + x^{2} y^{4} + x y^{5} + y^{6} + 1\right)$$
(x - y)*(1 + x^6 + y^6 + x*y^5 + y*x^5 + x^2*y^4 + x^3*y^3 + x^4*y^2)