The problem does not require you to solve that equation in general and I suspect it can't be. In (case i) you just have which can be separated as and can be integrated easily.
In (case ii) you have which, again can be separated: . The denominator on the left can be factored as and it can be integrated using "partial fractions".
In (case iii) you have which can be separated as . If you let then so and the left side becomes and the substitution reduces it even further. (which means I should have suggested to begin with!)