Correct option: (a) [(qn) / (p + q)] + 1
Explanation:
Tr+1 = ncr an–r br
∴ Tr+1 = ncr (a / xq)n–r (bxp)r = ncr an–r br ∙ xpr ∙ x–qn+qr
= ncr an–r br xpr–qn+qr
For constant term xpr–qn+qr = x0
i.e. pr + qr – qn = 0
∴ r = [(qn) / (p + q)] ⇒ r + 1 = [(qn) / (p + q)] + 1
∴ constant term is Tr+1 = T[1 + {(qn) / (p + q)}]
i.e. [{(qn) / (p + q)} + 1]th term.