The equation 0 = -u * u can be simplified to:
0 = -u^2
This equation is a quadratic equation. A quadratic equation can have zero, one, or two solutions, depending on the discriminant (the value inside the square root in the quadratic formula). In this case, the discriminant is:
Discriminant = b^2 - 4ac
Since the equation is in the form 0 = -u^2, we have a = -1, b = 0, and c = 0. Plugging these values into the discriminant formula:
Discriminant = 0^2 - 4(-1)(0) = 0 - 0 = 0
The discriminant is equal to zero. When the discriminant is zero, the quadratic equation has one real solution. So, the equation 0 = -u^2 has one solution, which is u = 0.