It is known that (r + 1)th term, (Tr+1), in the binomial expansion of (a + b)n is given by
Assuming that x5 occurs in the (r + 1)th term of the expansion (x + 3)8, we obtain
Comparing the indices of x in x5and in Tr +1,
we obtain r = 3
Thus, the coefficient of x5 is
