由題意可得：C(n,4)：C(n,2)=14：3
即：3C(n,4)=14C(n,2)
3n(n-1)(n-2)(n-3)/24=14n(n-1)/2
(n-2)(n-3)=56
n²-5n-50=0
(n-10)(n+5)=0
易解得：n=10
則展開式通項(xiàng)T(r+1)=C(10,r)*(∛x)^(10-r) *[1/(2∛x)]^r=(1/2)^r *C(10,r)*x的(10-2r)/3 次冪
令(10-2r)/3=2,解得：r=2
所以含x²的項(xiàng)為T3=(1/2)² *C(10,2)*x²=(45/2)*x²
而當(dāng)10-2r=0時(shí),得：r=5,則：T6=(1/2)^5 *C(10,5)*x^0=126
當(dāng)10-2r=-6時(shí),得：r=8,則：T9=(1/2)^8 *C(10,8)*x^(-3)=(45/256)*x^(-3)
所以展開式中的有理項(xiàng)有3項(xiàng),它們是：T3=(45/2)*x²,T6=126,T9=(45/256)*x^(-3)