Let n be a positive integer and a,b be non–zero real numbers.
(i) For (ax+xb)n, obtain an expression for the power of x occurring in the general term Tr+1 in terms of r.
(ii) Hence derive the condition that r must satisfy for Tr+1 to be independent of x.
(iii) Using the result of part (ii), find the independent term in (5x−x2)10.