To find the product of -2x^3+x-5 and x^3-3x-4, we need to multiply each term in the first polynomial by the second polynomial. (So, x^3 - 3x - 4) times ....
-2x^3 = -2x^6 + 6x^4 + 8x^3
x = x^4 - 3x^2 - 4x
-5 = -5x^3 + 15x + 20
If we add all these together, we get (-2x^6 + 7x^4 + 3x^3 - 3x^2 + 11x + 20)
