Question 737222
Hint:


Let z = x^3. So squaring both sides gives us z^2 = (x^3)^2 = x^6. This means


z = x^3


z^2 = x^6


-------------------------------------------------------


So 


x^6 + 56x^3 – 512 = 0


turns into


z^2 + 56z – 512 = 0


Your next task is to solve for z. I'll let you do this. You would use the quadratic formula to solve for z. 


Once you have 2 solutions for z, you then use each solution of z to find the solutions for x.