The question is as above. I have not learnt about the Wronskian or the likes.
I suppose that I'll have to do something with differentiation or trying different x values.
$a$ and $b$ are non-zero and not equal to each other. I should have mentioned this earlier.
I have not learnt about the Wronskian formally and doubt that I should use it. It is nice to learn new methods and new theorems, however.