Which expression is not a linear polynomial?

Correct answer: \(x^2+1\)

A linear polynomial has highest exponent 1 and is of the form \(ax+b\), where \(a\neq 0\). In \(x^2+1\), the highest exponent of \(x\) is 2, so it is a quadratic polynomial, not a linear polynomial. Although \(\frac{x}{4}-6\) has a fractional coefficient, its highest exponent of \(x\) is 1, so it is linear. Exam tip: To find the degree of a polynomial, identify the greatest exponent of its variable.