Determine the area of ​​a rectangle when its side lengths are ​[[$ 2x +1 $]]​ and [[$ 3x + 4 $]]​.

The area of the rectangle is the sum of the areas of the four smaller rectangles:

[[$ A = 6x^2+8x+3x+4=6x^2+11x+4 $]]​

On the other hand, the area can also be calculated as the product of the lengths of the rectangle's sides.

Answer: The area of ​​the rectangle is [[$ 6x^2+11x+4 $]]​.