Sn = [x^(1/2) - 1/3x]^10
第n项Tn = C10取n *x^(n/2)*(-1/3x)^(10-n) = (-1)^(10-n)* C10取n *x^(10-n/2)
含x的正整数指数幂的项数是T0=x^10,T2=45x^9,T4=210x^8,T6=210x^7,T8=45x^6,T10=x^5