## Precalculus: Concepts Through Functions, A Unit Circle Approach to Trigonometry (3rd Edition)

$(4x+3)^2$
The polynomial $16x^2 + 24x + 9$ is of the form $a^2+2ab+b^2=(a+b)^2$. Thus it is a complete square and we have $$16x^2 + 24x + 9=(4x+3)^2 .$$