The area of a square park is $$16x^2 + 8x + 1.$$ What is the length of the side of the park?

Let the length of the side of the square park = $$a$$

Area of the square park = $$a^2$$

Given,

Area of the square park = $$16x^2 + 8x + 1$$

$$=$$>  $$a^2=16x^2+8x+1$$

$$=$$>  $$a^2=\left(4x\right)^2+2\left(4x\right)+1^2$$

$$=$$>  $$a^2=\left(4x\right)^2+2.4x.1+1^2$$

$$=$$>  $$a^2=\left(4x+1\right)^2$$

$$=$$>  $$a=4x+1$$

$$\therefore\ $$Length of the side of the square park = $$4x+1$$

Hence, the correct answer is Option B