i'm not sure if the heading makes sense but i have a sample question that might make it clearer
$$x^4+ax^3+2x^2=0$$, if a is a real constant, when will the equation have one unique solution?
can you factorise out the x^2 and then divide 0 with x^2? or would you always use the null factor law when you carry out operations with x?
reaction for more information.