I used this model [y = D+(A-D)/(1+(x/C)^B)] and predicted all parameters using a vector of 'x' and 'y'. For a specific value of 'y', I would like to calculate a value for the 'x' using this model [x =((((D+(A-D))/y)-1)^1/B)*C] derived from the original model. But the calculated 'x' is not what it should be. I am assuming there is something wrong with this model [x =((((D+(A-D))/y)-1)^1/B)*C]. May someone give me a comment?