Left: the parabola $y = x^2 – 0.4$ has two real roots; its phantom is below the $x$-plane. Right: the parabola $y = x^2$ has a repeated root; it meets its phantom at this root.

Sean is a PhD student researching geophysical fluid dynamics at UCL. He studies coastal outflows, but so far has been unable to persuade the department to send him on a research trip to the beach.

More from Chalkdust

Both comments and trackbacks are currently closed.