Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(...)
Error, (in convert/RootOf) there is ambiguity in RootOf(...)
The error occurs when evalf or convert are passed expressions that have ambiguity in regards to specification of roots.
The numerical approximation of 12 used as a root selector is not helpful in distinguishing between the two roots, 12−52, 12+52, since both roots are a distance of exactly 52 from 12.
Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(_Z^2-_Z-1, 1/2)
Use a different value as the root selector:
The numeric selector, 0, is not sufficient to distinguish whether r1 is the positive or negative root. Therefore, the following gcd computation is ambiguous: if r1 represents the positive root, then the GCD is x−2, but if r1 represents the negative root, then the GCD is 1. Hence an error is raised:
Error, (in evalf/RootOf) there are ambiguous values encoded in RootOf(_Z^2-2, 0)
If you use a different selector that is not ambiguous, you can get an answer. Here, we use index=1 and index=2.
We've specified two distinct roots, and their gcd is 1.
Error, (in convert/RootOf) there is ambiguity in RootOf(_Z^2-_Z-1, 1/2)
This is the same root selector problem as in example 1. As was done for that example, by choosing a different numeric selector for the RootOf, the specification is no longer ambiguous:
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