=[5(2x+y)(2x-y)]/[(2x+y)(x-8y)]=5(2x-y)/(x-8y)=(10x-5y)/(x-8y)
5(4x^2-y^2)/(2x^2-15xy-8y^2) = 5(2x+y)(2x-y)/[(2x-y)(x+8y)]=5(2x+y)/(x+8y)