fundamental set whose Casoration is $\operatorname{C}(n)=-1$

Question

Show that the equation:

$$ \Delta^2 y(n)= p(n)y(n+1) $$

has a fundamental set of solutions whose Casoratian determinant $\operatorname{C}(n)=-1$.

(It is $\Delta y(n) = y(n+1)-y(n)$)

edit: I tried buy I can't find any idea how to approach this problem.

Any help?

Thank's in advance!