Answer:
x - 8y - z = 1
Step-by-step explanation:
Data provided according to the question is as follows
f(x,y) = z = ln(x - 8y)
Now the equation for the tangent plane to the surface
For z = f (x,y) at the point P
is

Now the partial derivatives of f are


= 1
Now

= -8
So, the tangent equation is

Now after solving this, the following equation arise
z = x - 9 - 8y + 8
z = x - 8y - 1
Therefore
x - 8y - z = 1
Divide both sides by -3, and replace
with
. Then

Factorize the quadratic in
to get

which in turn means

But
for all real
, so we can ignore the first solution. This leaves us with

If we allow for any complex solution, then we can continue with the solution we ignored:

Answer:
Slope is the difference between the y-coordinates divided by the difference between the x-coordinates.
Cost of visit per month is $414/12 = $34.5
Cost of individual visit per month = $34.5/8 = $4.3125
Negative 10 minus 12= is negative 22!!! hope it helps!!!