negative control in Q-PCR how to analyze results?
 

In our lab, we tried to quantify expression of a gene by q-pcr, Let's assume that the results are :

A: [1.52E6]
B: [6.54E6]
C: [7.84E6]
D: [9.82E6]
Negative: [3.10E6]

Is it appropriate to subtract the negative control from the obtained values? In case the negative control was subtracted from A, can we conclude that the gene could not be detected?(negative control is bigger than A)

thanks in advance