```Date: Oct 23, 2012 10:32 AM
Author: Dave L. Renfro
Subject: Re: MIT Math Diagnostic for Physics Placement

Dave L. Renfro wrote (in part):http://mathforum.org/kb/message.jspa?messageID=7910806>> Problem B2: Instead of saying "Find all possible values of x which>> solve the equation x^4 - 13x^2 + 36 = 0", I would be less vague and>> explicitly ask for all complex solutions.Robert Hansen wrote (in part):http://mathforum.org/kb/message.jspa?messageID=7911198> Doesn't that factor to (x^2 - 9)(x^2 - 4)? -> x = +/-3, +/-2Using "complex solutions" gives test takers making certainkinds of errors more rope to hang themselves with, althoughpersonally I consider something like x = +/- 3i, +/- 2i tobe better than something like x = +/-9, +/-4, which in turnis better than something like x = +/-13, +/-36. Ideally, I'dwant to see their work, but in the absence of that, for atotal of 5 points for this problem, I might give 3 pointsfor x = +/- 3i, +/- 2i and 1-2 points for x = +/-9, +/-4.Note that even x = +/-9, +/-4 suggests they correctly factoredand they recognized there will be two pairs of solutions.Dave L. Renfro
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