#### Answer

The well-known formula $\frac{-b+\sqrt{b^{2}-4 a c}}{2 a}$ contains a square root in it. The
square root of a number could have a big number of decimals or it could
be irrational and have an undefined amount of decimals. That's the case in
which it would not really be effectively computable. The algorithm will have
to specify how many decimals (at most) will be used for further calculations.