## Elementary and Intermediate Algebra: Concepts & Applications (6th Edition)

$prime$
Rearranging the terms, the given expression is equivalent to \begin{array}{l}\require{cancel} 47-42y+9y^2 \\\\= 9y^2-42y+47 .\end{array} Using the factoring of trinomials in the form $ax^2+bx+c,$ the $\text{ expression }$ \begin{array}{l}\require{cancel} 9y^2-42y+47 \end{array} has $ac= 9(47)=423$ and $b= -42 .$ There are no two numbers with a product of $c$ and a sum of $b.$ Hence, the expression above is $\text{ prime .}$