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

$(2x+3)^2$
The polynomial $4x^2+12x+9$ is of the form $a^2+2ab+b^2$, which is a complete square. That is, we have $$4x^2+12x+9=(2x+3)^2 .$$