а) (2a+b)(5a-b)-3a(2a+b) = 10a^2 - 2ab + 5ab - b^2 - 6a^2 - 3ab = 4a^2 - ab - b^2
б) (2x+7y)(2x-y)-7y(2x-y) = 4x^2 - 2xy + 14xy - 7y^2 - 14x^2 + 7xy = -10x^2 + 19xy - 7y^2
в) 2y^2(y+3)-4y(y+3) = 2y^3 + 6y^2 - 4y^2 - 12y = 2y^3 + 2y^2 - 12y
г) 27x^3(a-4x)-18x^2(4x-a) = 27ax^3 - 108x^4 - 72x^2 + 18ax^2 = 27ax^3 + 18ax^2 - 108x^4 - 72x^2
а) (2a+b)(5a-b)-3a(2a+b) = 10a^2 - 2ab + 5ab - b^2 - 6a^2 - 3ab = 4a^2 - ab - b^2
б) (2x+7y)(2x-y)-7y(2x-y) = 4x^2 - 2xy + 14xy - 7y^2 - 14x^2 + 7xy = -10x^2 + 19xy - 7y^2
в) 2y^2(y+3)-4y(y+3) = 2y^3 + 6y^2 - 4y^2 - 12y = 2y^3 + 2y^2 - 12y
г) 27x^3(a-4x)-18x^2(4x-a) = 27ax^3 - 108x^4 - 72x^2 + 18ax^2 = 27ax^3 + 18ax^2 - 108x^4 - 72x^2