SOLUTION: The demand equation for a certain product is given by p=5000(1-(4/(4+e^-0.002x))) Find the demands x for prices of a) p=$600 b) p=$400

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: The demand equation for a certain product is given by p=5000(1-(4/(4+e^-0.002x))) Find the demands x for prices of a) p=$600 b) p=$400      Log On


   



Question 373981: The demand equation for a certain product is given by
p=5000(1-(4/(4+e^-0.002x)))
Find the demands x for prices of
a) p=$600
b) p=$400

Answer by jsmallt9(3759) About Me  (Show Source):
You can put this solution on YOUR website!
p=5000%281-%284%2F%284%2Be%5E%28-0.002x%29%29%29%29
To find x for p = 600:
600+=+5000%281-%284%2F%284%2Be%5E%28-0.002x%29%29%29%29
We need "peel away" from the outside on the right side. First we get rid of the 5000 by dividing both sides be 5000:
600%2F5000+=+1-%284%2F%284%2Be%5E%28-0.002x%29%29%29
or
0.12+=+1-%284%2F%284%2Be%5E%28-0.002x%29%29%29
Next the 1 must go. Subtract 1 from each side:
-0.88+=+-%284%2F%284%2Be%5E%28-0.002x%29%29%29
Multiply (or divide) both sides by -1 to eliminate the minus sign:
0.88+=+4%2F%284%2Be%5E%28-0.002x%29%29
Next we'll eliminate the fraction by multiplying both sides by %284%2Be%5E%28-0.002x%29%29:
0.88%29%2A%284%2Be%5E%28-0.002x%29%29+=+4
Using the Distributive Property on the left side:
0.88%29%2A%284%29%2B%280.88%29%2Ae%5E%28-0.002x%29+=+4
3.52+%2B+%280.88%29%2Ae%5E%28-0.002x%29+=+4
Subtracting 3.52 from each side:
%280.88%29%2Ae%5E%28-0.002x%29+=+0.48
Divide by 0.88:
e%5E%28-0.002x%29+=+%280.88%29%2A0.48
e%5E%28-0.002x%29+=+0.4224
Now that the exponential part of the equation is isolated, we use logarithms to proceed. Since the base of the exponent is e, it is best to use base e logarithms (aka lm):
ln%28e%5E%28-0.002x%29%29+=+ln%280.4224%29
On the left side we can use a property of logarithms, log%28a%2C+%28p%5Eq%29%29+=+q%2Alog%28a%2C+%28p%29%29, to "move" the exponent out in front of the logarithm. (It is this property which is the very reason we use logarithms. It gives us a way to get the variable out of the exponent.) Using the property on the left side we get:
%28-0.002x%29ln%28e%29+=+ln%280.4224%29
By definition, ln%28e%29+=+1 so this becomes:
-0.002x+=+ln%280.4224%29
Last of all we divide by -0.002:
x+=+ln%280.4224%29%2F%28-0.002%29
This is an exact expression for your answer. Use your calculator if you want a decimal approximation:
x+=+%28-0.8618025465900853%29%2F%28-0.002%29
x = 430.9012732950426674
So for a price of $699 the demand will be approximately 431.

For a price of $400, replace the p with 400 and repeat these steps to find the demand at that price.