Answer:
[tex]y=4x^2+12x+9[/tex]
Step-by-step explanation:
Perform the square of the binomial, combine like terms, and then write the remaining expression in decreasing order of powers of x:
[tex]y=(2x+3)^2\\y=(2x+3)\,(2x+3)\\y=4x^2+6x+6x+9\\y=4x^2+12x+9[/tex]