Question

please give the solution to this question

Answer 1

Please remember the formula that relates vant hoff factor(i) with the degree of dissociation(α).
                                     i = 1 + (n-1)α
where 'n' is the number of ions present in the solution after dissociation.

For example, in A2B3 the number of particles in the solution after dissociation are 5 namely 2As and 3Bs. So, n=5
 
In your question the formula is AxBy, therefore there will be xAs and yBs in the solution after dissociation.
Hence here                               n = x + y

Now substitute it in the above equation, we get
                                       i = 1 + (x + y - 1)α
                                  i - 1 = (x + y -1)α

Therefore                       α = i - 1/(x + y-1)