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IsSurjective

check if a RINGHOM is surjective

Syntax 
IsSurjective(phi: RINGHOM): BOOL

Description
This function checks if a RINGHOM is surjective.

Example 
/**/  QQxyz ::= QQ[x,y,z];
/**/  QQab  ::= QQ[a,b];

/**/  Use QQab;
/**/  phi := PolyAlgebraHom(QQxyz, QQab, [a+1, a*b+3, b^2]);
ideal(-x^2*z +y^2 +2*x*z -6*y -z +9)
/**/  IsSurjective(phi);
false

/**/  PreImage(phi, b);
record[IsInImage := false, ker := ideal(-x^2*z +y^2 +2*x*z -6*y -z +9)]

See Also