Question

What are the solutions of the equation x6 – 9x3 + 8 = 0? Use u substitution to solve.

Answer 1

x6 – 9x3 + 8 = 0
let u = x^3
u^2 - 9u + 8 = 0 
(u-8)(u-1) = 0
u = 1,8
back substitute 
1 = x^3
8 = x^3

x = 1 , 2