1) (6a^2 + 5b^2)(2a^2-4b^2)
2)(-7m^2-8n^2)(-m^2+3n^2)
3)(4n^2-1)(n^2+5)
4)(8x^2-3xy)(3x^3-xy )
5)(5ab^2-4b^3)(3ab^3-4a^2)
6)(7x^3y^2-xy )(-2x^2y^2+5xy^3)