Why do this problem?
It gives learners experience of algebraic manipulation of
polynomials and working with surds. It is based on the fact that if
you know one root of a polynomial then you know one of its
factors.
Possible approach
This can be used as a lesson starter.
Key questions
We are looking for a polynomial in $x$, do you know any values of
$x$ that satisfy the polynomial?
If you have an expression involving surds what can you try in order
to get rid of the square roots?