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

$(x^2+2x+3)(a+1)$
Using factoring by grouping, the factored form of the given expression, $ax^2+2ax+3a+x^2+2x+3 ,$ is \begin{array}{l}\require{cancel} (ax^2+2ax+3a)+(x^2+2x+3) \\\\= a(x^2+2x+3)+(x^2+2x+3) \\\\= (x^2+2x+3)(a+1) .\end{array}