(-a-b)(2a-3b) = -2a^2 + 3ab - 2ab + 3b^2= -2a^2 + ab + 3b^2
(-7x-4y)(-5x+7y) = 35x^2 - 49xy + 20xy - 28y^2= 35x^2 - 29xy - 28y^2
(-a-b)(2a-3b) = -2a^2 + 3ab - 2ab + 3b^2
= -2a^2 + ab + 3b^2
(-7x-4y)(-5x+7y) = 35x^2 - 49xy + 20xy - 28y^2
= 35x^2 - 29xy - 28y^2