## College Algebra (11th Edition)

$8r^2+26rs-99s^2$
Using the $(a+b)(c+d)=ac+ad+bc+bd$ or the FOIL Method and the laws of exponents, the given expression, $(2r+11s)(4r-9s) ,$ simplifies to \begin{array}{l}\require{cancel} 2r(4r)+2r(-9s)+11s(4r)+11s(-9s) \\\\= 8r^2-18rs+44rs-99s^2 \\\\= 8r^2+26rs-99s^2 .\end{array}