## College Algebra 7th Edition

$x-7$
RECALL: (1) $(a+b)(c+d) = ac +ad + bc + bd$ (known as the FOIL method) (2) $(a-b)(a+b)=a^2-b^2$ Use the formula (1) above to multiply the first pair of factors, and use formula (2) to multiply the second pair of factors to obtain: $=[1\cdot2 + 1\cdot(-x) + x \cdot 2 + x\cdot(-x)] -(3^2 - x^2) \\=(2 -x+2x-x^2)-(9-x^2) \\=(2+x-x^2)-(9-x^2)$ Subtract each term of the subtrahend to obtain: $=2+x-x^2-9-(-x^2) \\=2+x-x^2-9+x^2$ Combine like terms to obtain: $=(2-9)+x+(-x^2+x^2) \\=-7+x \\=x-7$