Which expression is a polynomial but not a monomial?

Correct answer: \(x^2+4\)

\(x^2+4\) is a polynomial because the powers of the variable \(x\) are \(2\) and \(0\), both of which are non-negative integers. It has two terms, \(x^2\) and \(4\), so it is a binomial, not a monomial. \(5x^3\) is a polynomial with only one term, so it is a monomial. In \(\sqrt{x}+2\), the exponent of \(x\) is \(\frac{1}{2}\), while \(x^2+\frac{1}{x}\) contains exponent \(-1\); therefore, neither is a polynomial. Exam tip: Variable exponents in a polynomial must be \(0,1,2,\ldots\).