На вторую вроде что-то начал делать.
In[1]:=
t={0.5, 1, 2, 4, 8, 16}
Out[1]=
{0.5,1,2,4,8,16}
In[2]:=
y={0.95,0.80,0.62,0.45,0.2,0.04}
Out[2]=
{0.95,0.8,0.62,0.45,0.2,0.04}
In[5]:=
z=Log[y]
Out[5]=
{-0.0512933,-0.223144,-0.478036,-0.798508,-1.60944,-3.21888}
In[15]:=
Fit[{{0.5,-0.05},{1,-0.22},{2,-0.48},{4,-0.8},{8,-1.6},{16,-3.2}},{f},f]
Out[15]=
-0.200454 f