$\frac{(\Delta y)}{(\Delta x)}=\frac{2}{1}=2$

$-\frac{2}{3}$

$D$ en $F$ en $A$ en $E$.

It is negative.

$\frac{(2-6)}{(2-0)}=-2$

$0$

The points are at the same height, same $y$ -value.

P.e. on $[-1,0]$ with $\frac{(\Delta y)}{(\Delta x)}=\frac{(6-2)}{1}=4$

$t=0$ gives $T=90$ °C.

$\frac{\Delta T}{\Delta t}=\frac{T(5)-T(0)}{5-0}\approx \frac{\mathrm{49,95}-90}{5}\approx -\mathrm{8,8}$ °C/min.

Approximately 3,3°C/min.

The difference quotient become smaller, the coffee cools slower because the temperature difference between the coffe and the room becomes smaller.