Odpowiedź:
[tex]a)\ \ 2x+7y+5x-13y+4x-5y=11x-11y\\\\b)\ \ 3(4x+6b)-20x+8b=12x+18b-20x+8b=26b-8x\\\\c)\ \ 2x-7y-(5x-5y)=2x-7y-5x+5y=-3x-2y\\\\d)\ \ (2x-3y)(5c-3d)=10cx-6dx-15cy+9dy\\\\e)\ \ (4x+5y)(3y-2x)=12xy-8x^2+15y^2-10xy=2xy-8x^2+15y^2\\\\f)\ \ 5(x+1)(x-1)=(5x+5)(x-1)=5x^2-5x+5x-5=5x^2-5[/tex]