In this problem, s represents the whole domain of f(x), while f(t) represents the whole range of f(x).

All points (s, f (t))-(s, t∈D) form a square area,

This means that the length of the definition field is equal to the length of the entire value field.

Suppose that the two solutions of f(x)=0 are x 1, x2 (x 1

The length of the domain is x2-x 1.

Because f(x)=√ax? +bx+c(a