\(\left(x-\sqrt{2}\right)+3\left(x^2-2\right)\)
<=>\(\left(x-\sqrt{2}\right)+3\left(x-\sqrt{2}\right)\left(x+\sqrt{2}\right)\)
<=>\(\left(x-\sqrt{2}\right)\left[1+3\left(x+\sqrt{2}\right)\right]\)
<=>\(\left(x-\sqrt{2}\right)\left(1+3x+3\sqrt{2}\right)\)