Question 16
A quadratic function $f$ sends any interval $I$ of length 1 to an interval $f(I)$ of length at least 1.
Prove that for any interval $J$ of length 2, the length of the interval $f(J)$ is at least 4.
Prove that for any interval $J$ of length 2, the length of the interval $f(J)$ is at least 4.