Identify the variable expression that is not a polynomial?

A polynomial is an algebraic expression that is the sum of terms, each of which is a product of a constant coefficient and a non-negative integer power of a variable.

a) 3x + 2x^2 - 5

b) √x + 3

c) x^3 - 2x + 1

d) 4x^2 - 3x + 7

The answer is b) √x + 3.

The square root function is not a polynomial because it is not a power function. A power function is a function of the form f(x) = x^n, where n is a non-negative integer.