Answer:
the first three are polynomials; the remainder are not
Explanation:
A polynomial is a sum of terms with non-negative integer powers of the variables.
The first three expressions are all polynomials; the last three are not.
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The rational expression with a variable in the denominator is a "rational function", but is not a polynomial. The expressions containing |x| and √x are not expressions that have x to an integral power.
The coefficients of the polynomials we generally deal with are usually integers or fractions. However, there is no requirement that they be rational or real. The second expression is still a polynomial even though it has irrational coefficients.