The area of a square park is 16x2 + 8x + 1. What is the length of the park?

Answer: Option B

Let the length of square park = L
Area = L²
L² = 16x² + 8x + 1
Length of the park
$$\begin{array}{rl}& =\sqrt{16x^2+8x+1}\\ & =\sqrt{{\left(4x\right)}^2+2\times 4x+1^2}\\ & =\sqrt{{\left(4x+1\right)}^2}\\ & =\left(4x+1\right)\text{ units}\end{array}$$