is a linear polynomial
S<u>tep-by-step explanatio</u>n:
based on the highest power of the variables of a polynomial, it can be classified as linear,polynomial, quadratic polynomial,cubic polynomial etc.
In a linear polynomial, the highest power of the variable is 1. The general form of a linear polynomial is ax+b
In a quadratic polynomial, the highest power of the variables is 2.The general form of quadratic polynomial is 
In a cubic polynomial,the highest power of variable is 3.The general form of cubic polynomial is
.
Take the given question and simplify it

It is of the form ax+b. Hence it is a linear polynomial.