Rozhodnìte, zda  následující dvojice $(P,\rho)$ tvoøí metrický
prostor:
\roster
\item"a)" $P = \Bbb R^n, \, \rho(x,y) = \max \{|x_i-y_i|;\, 1
\leq i \leq n \},$
\item"b)" $P = \Bbb R^n, \, \rho(x,y) = (\sum_{i=1}^{n}
|x_i-y_i|^2)^{\frac 12},$
\item"c)" $P = \Bbb R^n, \, \rho(x,y) = \sum_{i=1}^{n}
|x_i-y_i|,$
\item"d)" $P = \Cal C ([0,1]), \, \rho(f,g) = \sup \{|f(x)-g(x)|;
x \in [0,1]\},$
\item"e)" $P = \Cal C ([0,1]), \, \rho(f,g) =
\int_0^1|f(x)-g(x)|\text{dx},$
\item"f)" $P$ je neprázdná množina, $\rho(x,y) = 1,$ pokud $x \not
= y,$ $\rho(x,y) = 0,$ pokud $x=y,$
\item"g)" $P = \Bbb R^n, \, \rho(x,y) = (\sum_{i=1}^{n}
|x_i-y_i|^{\frac 12})^2.$
\endroster
