how do you factor 2x^4-14x^2+24 ?
Divide by 2, and then recognize that it can be written as a quadratic equation in x^2. That expression can be factored into two terms that are the differences of squares.
2(x^4 -7x^2 +6) = 2(x^2-1)(x^2-6)
= 2(x+1)(x-1)(x+sqrt 6)(x - sqrt 6)