Answer:
[tex]12x {}^{2} + 4x[/tex]
Step-by-step explanation:
Ok, so to find the area of a square or a rectangle we need to multiply the width by the height. Since we now both, we can create an expression.
[tex](3x + 1) + (4x)[/tex]
So now we can apply the distributive law/property to expand the expression.
[tex]3x(4x) + 1(4x)[/tex]
Finally, simplify.
[tex]12x {}^{2} + 4x[/tex]
