Question

solve by u-substitution x^6-9x^3=-8

Answer 1

let u = x^3
therefor the equation turns to
u^2-9u=-8
u^2-9u+8=0
(u-8)(u-1)=0
now we have u=8 or u=1
now you can put x^3 back into the u position
x^3=8 or x^3=1
then you can solve the problem from there :) let me know if that made sense or not

Answer 2

\(\bf {\color{blue}{ x^6\implies (x^3)^2\qquad \qquad u=x^3}}
\\ \quad \\ \quad \\

x^6-9x^3=-8\implies (x^3)^2-9x^3+8=0\implies {\color{blue}{ u}}^2-9{\color{blue}{ u}}+8=0\)

Answer 3

Thank you so much, i was stuck at how to make it equal to zero, but now i can solve from here. Thanks!

Answer 4

yw

Answer 5

And then, of course, keep factoring. You're nowhere near done!

Answer 6

Glad to help!!!