Chapter 5 Polynomials and Polynomial Functions - 5.1 Use Properties of Exponents - 5.1 Exercises - Skill Practice - Page 334: 40

$A=\dfrac{x^2 \sqrt 3}{36}$

To calculate the area the formula is given as follows: $A=\dfrac{\sqrt 3}{4}s^2$ Length of the side of the triangle is $s=\dfrac{x}{3}$ Now, $A=\dfrac{\sqrt 3}{4}s^2=\dfrac{\sqrt 3}{4}(\dfrac{x}{3})^2$ This gives: $A=\dfrac{\sqrt 3}{4}(\dfrac{x^2}{9})=\dfrac{x^2 \sqrt 3}{36}$