If you take A-math, you can easily use discriminant to solve. For E-math, you have to realise that this quadratic curve is U-shaped and therefore has a minimum point. If the minimum point lies above the x-axis, then it means that there is no solution, if it lies on the x-axis -- 1 solution, and if it lies below the x-axis -- 2 solutions. So the solution is just to complete the square and get the coordinates of the min point and prove where it lies on the xy-plane.