Question 995798
'
y = {{{p/q}}},


where  p  and  q  are functions of  x.


The formula for the differential of a quotient is 


dy = {{{(dp*q - p*dq)/q^2}}}.               (1)


You should know this formula.  In our case 


p = {{{2-v^2}}}, q = {{{2+v^2}}}.         (2)


So,  express now  dp  and  dq  based on formulas  (2)  and then substitute it into  (1).