We can simply multiply the roots together to find the original function.
(x + 2)(x - 4)(x - 4)(x - 3)
FOIL.
x^2 - 4x + 2x - 8(x - 4)(x - 3)
Combine like terms.
x^2 - 2x - 8(x - 4)(x - 3)
FOIL.
x^3 - 2x^2 - 8x - 4x^2 + 8x + 32(x - 3)
Combine like terms.
x^3 - 6x^2 + 32(x - 3)
FOIL.
x^4 - 6x^3 + 32x - 3x^3 + 18x^2 - 96
Combine like terms.
x^4 - 9x^3 + 18x^2 + 32x - 96 is the original function with the given roots.
