Write polynomial functions given its roots

Write a polynomial function of least degree with integral coefficients and have zeros 2, 1, -1.

Write a polynomial function of least degree with integral coefficients and have zeros 4, - 1, 6

Write a polynomial function of least degree with integral coefficients and have zeros 3, - 1, 1, 2

Write a polynomial function of least degree with integral coefficients and have zeros 2, - 2, 3, - 4

Write a polynomial function of least degree with integral coefficients and have zeros -2, 5, -3i, 3i

Write a polynomial function of least degree with integral coefficients and have zeros 4, -4, i, -i

Write a polynomial function of least degree with integral coefficients and have zeros - 4, 4 + i, 4 - i

Write a polynomial function of least degree with integral coefficients and have zeros -3, 1, 2i, -2i

Write a polynomial function of least degree with integral coefficients and have zeros - 2, 2, 3 - i, 3 + i

Write a polynomial function of least degree with integral coefficients and have zeros - 5, 4, 4 - i, 4 + i