Chapter 5 - Sections 5.1-5.7 - Integrated Review - Operations on Polynomials and Factoring Strategies - Page 313: 57

$A = 9 - 4x^{2} = (3+2x)(3-2x)$

Area of the square whose side is $3$ $= 3^{2} = 9$ Area of the square whose side is $x$ $= x^{2}$ Area of the shaded region $= 9 - 4 \times x^{2}$ $= 9 - 4 x^{2}$ To factorize, it is in the form of $a^{2} - b^{2}$. $a^{2} - b^{2} = (a+b)(a-b)$. $= 9 - 4 x^{2}$ $= 3^{2} - (2x)^{2}$ $= (3+2x)(3-2x)$