(3х-4y)^2-(2х7y)(4x+2y)=9x-24xy+16y^2-(14xy)(4x+2y)=9x-24xy+16y^2-(56x^2y+28xy^2)=9x-24xy+16y^2-56x^2y-28xy^2
(3х-4y)^2-(2х7y)(4x+2y)=9x-24xy+16y^2-(14xy)(4x+2y)=9x-24xy+16y^2-(56x^2y+28xy^2)=9x-24xy+16y^2-56x^2y-28xy^2