Answer
$4x^2+12x+9-16y^2$
Work Step by Step
The product of a binomial sum and a binomial difference is: $(A+B)(A-B)=A^2-B^2$.
The square of a binomial sum is: $(A+B)^2=A^2+2AB+B^2$.
The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$.
Hence here: $[(2x+3)+4y][(2x+3)-4y]=(2x+3)^2-(4y)^2=(2x)^2+2\cdot2x \cdot3+3^2-16y^2=4x^2+12x+9-16y^2$
