(3x^2 - y^2)^2 (-4a^3 + 0.5b)^2 = (9x^4 - 6x^2y^2 + y^4) (16a^6 - 4a^3b + 0.25b^2) = 144x^4a^6 - 36x^4a^3b + 2.25x^4b^2 - 96x^2a^6y^2 + 24x^2a^3by^2 - 1.5x^2b^2y^2 + 16a^6y^4 - 4a^3by^4 + 0.25b^2y^4