(x-3)(x-5)(x-6)(x-10)-24x ²
=[(x-3)(x-10)][(x-6)(x-5)]-24x ²
=($x^{2}$-10x+3x+30)($x^{2}$-5x-6x+30)-24x ²
=($x^{2}$-7x+30)($x^{2}$-11x+30)-24$x^{2}$
=[($x^{2}$-9x+30)+2x][($x^{2}$-9x+30)-2x]-24$x^{2}$
Đặt $x^{2}$-9x+30=y, khi đó:
(y+2x)(y-2x)-24$x^{2}$
=$y^{2}$-4$x^{2}$-24$x^{2}$
=$y^{2}$-28$x^{2}$
=$y^{2}$-$(2\sqrt[]{7}.x)^{2}$
=(y-2$\sqrt[]{7}$.x)(y+2$\sqrt[]{7}$.x)
=($x^{2}$-9x+30- 2$\sqrt[]{7}$.x)($x^{2}$-9x+30+2$\sqrt[]{7}$.x)
=...
