Explanation:
Polynomials of degree 1, aka linear polynomials, are the highest allowed for the divisor when using synthetic division. If the divisor is degree 2 and larger, then you'll need to use polynomial long division instead.
An example divisor of degree 1 is something like [tex]x+5[/tex], which can be written as [tex]x^1+5[/tex]. That exponent of 1 determines the degree.