pol = -1 + (x - x0)^2/a^2 + (2 (x - x0) x0)/a^2 + x0^2/
a^2 + (y - y0)^2/b^2 + (2 (y - y0) y0)/b^2 + y0^2/b^2
For the polynomial above, there is a relation:
rel = x0^2/a^2 + y0^2/b^2 == 1
How can I use this relation rel to replace the three terms x0^2/a^2 + y0^2/b^2 - 1 in the polynomial pol with 0, while keeping the other terms unchanged, to obtain the following final result:
(x - x0)^2/a^2 + (2 (x - x0) x0)/a^2 + (y - y0)^2/b^2 + (
2 (y - y0) y0)/b^2
