well, let's take a peek at each term's degree then [tex]\bf 4x^2y+5xy\iff 4x^2y^1+5x^1y^1\qquad
\begin{cases} & degree\\
4x^2y^1\to 2+1\to &3\\\\
5x^1y^1\to 1+1\to &2
\end{cases}[/tex]
notice, the degree of a polynomial, is from the exponent value of their variables
