MathDB
Parabola and lines

Source: 2021 Simon Marais, A1

November 2, 2021
conicsparabolacalculus

Problem Statement

Let a,b,ca, b, c be real numbers such that a0a \neq 0. Consider the parabola with equation y=ax2+bx+c, y = ax^2 + bx + c, and the lines defined by the six equations \begin{align*} &y = ax + b,   & y = bx + c, \qquad   & y = cx + a, \\ &y = bx + a,   & y = cx + b, \qquad   & y = ax + c. \end{align*} Suppose that the parabola intersects each of these lines in at most one point. Determine the maximum and minimum possible values of ca\frac{c}{a}.