I solved for y, and if d>0 i plot two y's and if d<0 i don't plot.
(d=b^2-4*a*c)
I made a "solve" function that takes two matrices (one square and one vector) and does Gauss-Jordan, but currently
it does not do row exchange so singular matix would give infinite values.
Edit:
The point was not to draw ellipse because there are simpler and faster ways,
but to experiment what problems I can solve with equation with terms with coefficients.
For example if I have system of two equations I can map a texture.