1、-8（x-3)^3=27 => (x-3)^3=-27/8 => x-3=-3/2
x=3/2
2、(2x-1)^3=8 => 2x-1=2 => x=1/2
3、340+512x^3=-3 => 512x^3=-343 => x^3=-343/512
x=-7/8