question_answer

If the roots of the equation \[{{x}^{3}}\text{-}12{{x}^{2}}\text{+}39x-28\text{ }=\text{ }0\]are in A.P., then their common difference will be

A)  \[\pm 1\]                      

B)  \[\pm 2\]          

C)  \[\pm 3\]           

D)  \[\pm 4\]