## Introductory Algebra for College Students (7th Edition)

-21x$^2$+7
The two sets of parentheses contain special products that result in the difference of the squares of the two terms of each set. (2x+3)(2x-3)-(5x+4)(5x-4) [(2x)$^2$-(3)$^2$]-[(5x)$^2$-(4)$^2$] (4x$^2$-9)-(25x$^2$-16) 4x$^2$-9-25x$^2$+16 (4x$^2$-25x$^2$)+(-9+16) -21x$^2$+7