MathDB
Points between parabolas

Source: St Petersburg 2022 9.4

September 28, 2022
parabolaalgebra

Problem Statement

We will say that a point of the plane (u,v)(u, v) lies between the parabolas y=f(x)y = f(x) and y=g(x)y = g(x) if f(u)vg(u)f(u) \leq v \leq g(u). Find the smallest real pp for which the following statement is true: for any segment, the ends and the midpoint of which lie between the parabolas y=x2y = x^2 and y=x2+1y=x^2+1, then they lie entirely between the parabolas y=x2y=x^2 and y=x2+py=x^2+p.