Answer this question: https://web2.0calc.com/questions/irrationality-proof
This page is going to help you! https://math.stackexchange.com/questions/2049981/create-a-monic-polynomial-with-integer-coefficients-with-sqrt32-sqrt33
Hope this does help!
I'm going to use "crt" to represent the cube root.
Also, I'm going to use this formula: (a - b)3 = a3 - 3a2b + 3ab2 - b3
y = [ x - ( crt(2) + crt(4) ]3
= x3 - 3·x2·( crt(2) + crt(4) ) + 3·x·( crt(2) + crt(4) )2 - ( crt(2) + crt(4) )3
= x3 - 3·crt(2)·x2 - 3·crt(4)·x2 + 3·crt(4)·x + 12·x + 6·crt(2)·x - 6 - 6·crt(2) - 6·crt(4)