Here's the question you clicked on:
dpflan
Can someone help explain "Newton's method"?
it is method for finding approximately solution of equation f(x)=0. You pick some starting point and then you compute tangent line to the f(x) in this point. Then you repeat these steps, but now picking point where tangent line=0 (crossed x-axis) as your starting point.
http://upload.wikimedia.org/wikipedia/commons/e/e0/NewtonIteration_Ani.gif
It is very fast approximation method, but be careful. It can easily fail to find the solution.