# Chapter 5 - Review: 75

The area of the rectangle is $9y^2-49z^2$ square units.

#### Work Step by Step

The area of a rectangle is given by the formula A=(length)(width). The rectangle has a length of $3y+7z$ and a width of $3y-7z$, use the formula above to find the area and have: $\\A = (3y+7z)(3y-7z)$ RECALL: $(a-b)(a+b)=a^2-b^2$ Use the formula above with $a=3y$ and $b=7z$ to have: $\\A=(3y)^2-(7z)^2 \\A=9y^2-49z^2$

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