Simple, use a calculator which gives answers to 6 significant figures.

Alternatively, you an use the Newton-Rafson convergence method. For example the roots of 3x

^{3} + x

^{2} - 5x + 3 can be found by finding out that

x = 3 / (3x

^{2} + x - 5) therefore use the series x = 3 / (3x

_{n-1}^{2} + x

_{n-1} - 5)

and letting x = any number. The series should converge to a point which is known as the root.

This is how a calculator computes the root of something too by the way.

What's my prize??