Question 907265
Find the roots using Rational Roots Theorem.  You want REAL roots.  The inequality could have up to three different roots.  Possible roots to check are -15, -5, -3, -1, 1, 3, 5, 15.


Only one root should be found, only one REAL root, that is.
The real root is x=5.  The inequality intersects the x axis at x=5.  Check the sign of the left member cubic expression to the left and to the right of x=5.