[tex]\bf \stackrel{\stackrel{degree}{\stackrel{2+5=7}{\downarrow }}}{-3a^2b^5}+\stackrel{\stackrel{\stackrel{degree}{1}}{\downarrow }}{2a^1}\impliedby \begin{array}{llll} \textit{highest degree of any term is 7}\\ \textit{so is a 7 degree polynomial}\\ \textit{or called a "septic"} \end{array}[/tex]
bear in mind that the degree of a polynomial comes from the highest degree of any of its terms, and the degree of a term is the sum of all exponents in the variables.
