A fraction can only equal zero if the numerator=0. Think about this. If the numerator is any other value, the fraction will have a value different from 0.
Let and let's multiply both sides of the equation by q, which of course is allowed
This shows only the numerator must be 0
Surely you can solve that
One word of caution, you need to be sure that the value you get does not make the value of the denominator=0. For example, if you solve that and got x=2 (this is not the answer), then the denominator would be 0, which isn't allowed. We also can't have negative numbers under the radical, but actually 0 divided by a complex number is still zero, so we shall not worry about such circumstances for this problem