(a+b)*(a-b)=a^2-b^2
(2x + y) * (2x -y)=(2x)^2-y^2=4x^2-y^2
sau
(2x + y) * (2x -y)= 2x*2x-2xy+2xy-y^2=4x^2-y^2
sper ca te-am ajutat
[tex](2x+y)(2x-y) =\big[(2x)+y\big]\big[(2x)-y\big] = (2x)^2-y^2 = 4x^2-y^2[/tex]
