Cubic Curves
1. Stating the problem: We are given two equations involving cubic terms:
$$7x^3 - 3y^3 + 5xy - 2x - 27 = 0$$
and
$$7x^3 - 7y^3 = 2(x - y)$$.
2. Simplify the second equation:
$$7x^3 - 7y^3 = 2(x - y) \implies 7(x^3 - y^3) = 2(x - y)$$.
3. Factor the cubic difference in the second equation:
$$x^3 - y^3 = (x - y)(x^2 + xy + y^2)$$,
thus
$$7(x - y)(x^2 + xy + y^2) = 2(x - y)$$.
4. If $x \neq y$, we can divide both sides by $(x - y)$:
$$7(x^2 + xy + y^2) = 2$$,
which describes a conic section.
5. Now consider the first equation:
$$7x^3 - 3y^3 + 5xy - 2x - 27 = 0$$.
It is a cubic curve with terms combining $x$ and $y$ in nonlinear ways.
6. To analyze both together, one can consider the system:
$$\begin{cases} 7x^3 - 3y^3 + 5xy - 2x - 27 = 0 \\ 7(x^3 - y^3) = 2(x - y) \end{cases}$$.
7. Graphically, these represent two cubic curves intersecting symmetrically about the origin, creating intricate looping shapes.
Final understanding: The curves describe implicit relationships in $x$ and $y$ with cubic terms, where the second equation simplifies to $7(x - y)(x^2 + xy + y^2) = 2(x - y)$, leading to the conic condition $7(x^2 + xy + y^2) = 2$ when $x \neq y$.