There are four paths from a city to the top of nearby mountain. Find the number of
possible treks from the city to the mountain and back, if it is required to use one
path up and another one down.
How many points of symmetry there exist for a rhombus? A rhombus -- opposite sides are parallel and all sides have equal length. (A point is a point of
symmetry of the rhombus if the reflection through this point maps the rhombus into
itself.)
Given the function \(g\) (see the picture),
find \(\lim _{x\to \infty }g(x)\).
\[
g(x)=\begin{cases}
-\frac12(x-1)^2+2 & \text{if } x < 1,\\
\frac2{x^2}+1 & \text{if } x \geq 1
\end{cases}
\]