问答题 <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20241014/14292671_0.png">展开式的二项式系数之和比<img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20241014/14292671_0_1.png">展开式的二项式系数之和小240．<br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20241014/14292671_0_2.png">展开式的第3项；<br/> <img border="0" alt="" src="https://tuku.weimei168.com/uploads/upimg/20241014/14292671_0_3.png">展开式的中间项．