Solution

ID: past-exam-of-the-mathematics-course-of-the-university-of-cambridge/2016/iii/paper-104/6/d/ii/solution

Part (c) shows that every finitely presented group embeds in a finitely presented group with no nontrivial finite quotients of a group. Consequently this property also has no possible forbidden witness . Therefore
Both properties have positive witnesses, for example and the trivial group respectively. It is the required embedding obstruction that fails in each case.

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