Question 138
A quadratic function $f$ has the property: for every interval $I$ of length 1, the interval $f(I)$ has length at least 1. Show that, for every interval $J$ of length 2, the interval $f(J)$ has length at least 4.
MathNet 2015-part-04 — 191 problems (EN–VI) Question 138
Math Olympiad Vault · MathNet 2015-part-04 — 191 problems (EN–VI)