Nalezn�te absolutn� extr�my funkce $f$ na mno�in� $M$.
$$
f(x,y) = x^2 - xy + y^2, \qquad
M = \{[x,y] \in \Bbb R^2; \, |x| + |y| \leq 1\}; \\
$$

$$
f(x,y) = \frac xa + \frac yb, \qquad M = \{[x,y]; \, x^2 + y^2
\leq 1\}, \qquad a > 0, \, b> 0.
$$
