Given:

To determine f'(-4), we first find the derivative of the given equation as shown below:

Next,we plug in x=-4 into f'(x)=6x-7:

Hence, the value of f'(-4) is equal to -31.
Then, we also note that we can find the slope by plugging in x=-4 into f'(x)=6x-7.
Hence, the value of m is: -31

Then,we use the point slope form:

where:
m=slope=-31
(x1,y1)=point=(-4,81)
We plug in what we know:

Since the equation of the tangent line can be written in y=mx+b, the value of b is equal to -43.
Therefore, b is: -43