Two arithmetic progressions have first terms a1,a2 and common differences d1,d2 respectively.
a. (i) Write the general expression for the n-th term of each progression using the given symbols.
b. (ii) If the n-th terms of the two progressions are equal, obtain the relation connecting n,a1,a2,d1 and d2.
c. (iii) Explain the condition on d1 and d2 under which such an n can exist as a positive integer.