If the constant term in the binomial expansion of x2−1xn,n∈N is 15, then the value of n is equal to_____.

Tr+1=nCrx2n−r(−1)rx−r        =nCrx2n−3r(−1)rConstant term =nCr(−1)r if 2n=3r i.e., coefficient of x=0Hence,  nC2n/3(−1)2n/3=15=6C ,n=6