Question: accept only simplified answer in MapleTA

Suppose I have a questions that says simplify some random square root

using the algorithm

$ques_ML=maple("f := $ques_exact: XMLTools[Print](MathML[Export](f));");

How do I create an answer field that ONLY allows the student to provide the simplified answer $ques_ML??  How might I provide partial points if they do not simplify (for a classic pythag triangle question for example)?

Thank you

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