The problem occurs inside the log parenthesis. The syntax that you have used tells Matlab to solve the equation:
for x. Check the documentation for mrdivide to get more a thorough explanation. If you want to do element-wise arithmetic operations (division, power, etc.) then you have to use . before each operation. Look for more information here.
In your case you have to modify your equation:
Here the log function computes the natural logarithm.
Here the log10 function computes the logarithm when the base is 10
For example if:
the result is: