data={{Log[1/4],Log[15]},{Log[1/8],Log[45]},
{Log[1/16],Log[127]},{Log[1/32],Log[345]}}

N[{{-Log[4],Log[15]},{-Log[8],Log[45]},{-Log[16],Log[127]},{-Log[32],Log[345]}}]

N[data]

line = Fit[data, {1,x},x]

Show[ListPlot[data, PlotStyle->Red, AspectRatio->Automatic], Plot[line, {x, -5,0}, PlotStyle->Green]]