I was wondering if at any point you considered a version of the puzzle where the gaps were both above and below the Xs, so that MOVE BOTH XS VERTICALLY required knowing the roots, and not just blindly shifting the Xs into the only free squares.

Although that questions presupposes you intended the movement to be made without appreciation for the actual values, which is how I took it at the time, so a second question (inspired by my expectation of being marked wrong): I (mis)read the preamble as indicating that the instructed move, made in discrete units of whole squares, would result in a (reasonably) accurate plot of the solution. Reading other blog posts on this site I now think you intended that the solver aim for the proper points in the target squares to represent +/- 6.1, requiring knowledge of the roots after all. (Annoyingly I had the roots but was working in whole squares when I made the move.)

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