Let q(x)=ax4+bx3+cx2, where a, b and c are non-zero integers.
(i) Show that x2 is a common factor of q(x).
(ii) Prove that x2 is the greatest common factor of q(x) if and only if a, b and c have no common factor other than 1.
(iii) Suppose now that a=8, b=12 and c=20. Find the GCF of the coefficients, and then factorise q(x) completely.
(iv) Using the factorised form from part (iii), solve q(x)=0.