\(5xy\left(2x^3y^2-7xy+3y\right)=10x^4y^3-35x^2y^2+15xy^2\\ \left(-6x^6+15x^2-4x^4\right):3x^2=-2x^4+5-\dfrac{4}{3}x^2\\ \left(x^2-y^2-12x+36\right):\left(x+y-6\right)\\ =\left[\left(x-6\right)^2-y^2\right]:\left(x+y-6\right)\\ =\left(x-y-6\right)\left(x+y-6\right):\left(x+y-6\right)\\ =x-y-6\)