SOLUTION: Consider a function F(x)= x^3 -x^2 -x -8. If F(u)= -8,how many real values of u are there?

Algebra ->  Test -> SOLUTION: Consider a function F(x)= x^3 -x^2 -x -8. If F(u)= -8,how many real values of u are there?       Log On


   

Question 1040850: Consider a function F(x)= x^3 -x^2 -x -8. If F(u)= -8,how many real values of u are there?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
F%28x%29=+x%5E3+-x%5E2+-x+-8 and F(u) = -8
==> F%28u%29=+u%5E3+-u%5E2+-u+-8+=+-8
==> +u%5E3+-u%5E2+-u+=+0 ==> u%28u%5E2-u-1%29+=+0
==> the roots are u = 0, u+=+%281+%2B-+sqrt%285+%29%29%2F2+.
==> there are three real values for u.