Let's log 10 on both side of the equation for both of your equations
You'll get log y = ( x-3 )log 8
and log y = x log 8
Lets assume that a graph of log y against x is plotted.Then log y becomes the y variable, log 8 becomes the gradient and x becomes the x variable. To make visualizing easier, lets assume the gradient is m=log 8= 1.
So the two log equation becomes,
y= x
and
y= x-3
Thus, from the x intercept we can see that the graph of y = 4(2)^x-3 is translated from the graph y=4(2)^x 3 units down .