（5x+3y）(3y-5x)-(4x-y)(4y+x)
=（3y+5x）(3y-5x)-(4x-y)(x+4y)
=9y^2-25x^2-(4x^2+16xy-xy-4y^2)
=9y^2+4y^2-25x^2-4x^2-15xy
=13y^2-29x^2-15xy