1. The general way to solve equations with square-roots is:

square - isolate remaining square-roots on one side - square - isolate remaining square-roots on one side - square - isolate remaining square-roots on one side - square .... until there is no square-root left.

2. You'll get finallya quadratic equation in a. Solve for a.

3. Afterwards solve these 2 equations for x.

4. Since you may transform a false equation into a true one by squaring you must check if your results satisfy the given original equation.