sentences:  Given this, use a root-finding algorithm (such as the bisection method) to find the value "x"1 which produces "y""n"−1 as close to "f"(0) as possible.Alternatively, look for the value which makes the area of the topmost layer, "x""n"−1("f"(0) − "y""n"−1), as close to the desired value "A" as possible.This saves one evaluation of "f" −1("x") and is actually the condition of greatest interest.