How is multiplying radical
expression similar to FOIL with
binomials?
(ax+by)(cx+dy)
= (ac)x^2 + (ad+bc)xy + (bd)y^2
(a√x + b√y)(c√x + d√y)
= (ac)x + (ad+bc)√(xy) + (bd)y
for example
(2x-3y)(3x+y) = 6x^2+7xy-3y^2
(2√7 + 3√5)(√7 - 2√5)
= 2*7 + (3-4)√(7*5) - 6*5
= 14 - √35 - 30
= -16 - √35