According to the rational root theorem, what are all the potential rational roots of f(x) = 9x4 – 2x2 – 3x + 4?

The coefficients of x4 is 9. It has factors of 1, 3, and 9. The constant is 4. It has factors of 1, 2, and 4.
The (positive and negative) ratios of the factors of the coefficient of the x4 and the constant 4 are the potential rational roots of the function.
The answers are:
1, -1, 3, -3, 9, -9, 1/2, -1/2, 3/2, -3/2, 3/4, -3/4, 9/2, -9/2, 9/4, -9/4