The number of rational terms in the expansion of is
A term in the expansion of is
of the form
This term will be rational if and are both rational numbers. This is possible if and only if is multiple of and s is a multiple of Possible values of r are and 6 whereas the possible values of are and Also note
that
For can take value or
For can take value 0 or
For can take value
For can take value
Thus, the number of rational terms is