5) 8x² - 48xy + 192y²; 6) -756a⁶ + 306a⁴ - 8a²; 7) 2x⁶ - 16y³;

5) $$8x^2 - 48xy + 192y^2 = 8(x^2 - 6xy + 24y^2)$$ 6) $$-756a^6 + 306a^4 - 8a^2 = -2a^2(378a^4 - 153a^2 + 4)$$ 7) $$2x^6 - 16y^3 = 2(x^6 - 8y^3) = 2((x^2)^3 - (2y)^3) = 2(x^2-2y)(x^4+2x^2y+4y^2)$$