-2x3 - 10x2 - 12x = -2x*(x2 + 5x + 6) = -2x*(x + 2)*(x + 3)
For a start, you can look for a common factor, and separate it. What remains (the other factor) will only be a polynomial of degree 2; I assume you already learned how to factor that.
(4x - 3)(16x^2 + 12x + 9)
4x(4x^2 + 3x + 1)
The answer is (2x^2+3)(4x+1)
With the help of the quadratic equation formula
(x + 4)(x - 2)(x - 2) or (x + 4)(x - 2)2
4x + 20