Multiplicación de binomios...

(a + b) . (x + y) = = a . (x + y) + b . (x + y ) = ax + ay + bx + by – (a + b) . (a – b) = = a . (a – b) + b . (a – b) = aa – ab + ba – bb = a2 - ab + ab – b2 = a2 –...