| 下面有4个关于复数的类比推理： ①复数的加减运算可以类比多项式的加减运算； ②由向量
③由向量的性质|
④由向量加法的几何意义可以类比得到复数加法的几何意义． 其中结论正确的是______．（写出所有符合要求的序号） |
复数的加减法运算可以类比多项式的加减法运算法则，①正确
由向量的性质|
|2=a
2类比得到复数z的性质|z|2=z2，这两个长度的求法不是通过类比得到的．故②不正确，a
由向量三角不等式可以类比得到复数三角不等式．故③正确．
由向量加法的几何意义可以类比得到复数加法的几何意义．故④正确．
故答案为：①③④．
| Air France SA said Monday that its second-quarter net profit fell 35 percent to 57 million ($57.4 million), but sales were steady and operating profit surged. Earnings before interest and tax, a measure of operating income, gained 86 percent to 141 million as fuel costs fell and cargo traffic rose. Air France has been hurt less than rivals such as British Airways PLC and Lufthansa AG by the slowdown on North Atlantic routes following the war on Iraq in 2003 because it has fewer flights in that market. Net income fell as the airline paid deferred taxes that came due. Sales rose 0.9 percent to 3.2 billion. The carrier lost about 80 million in revenue because of a four-day strike by pilots in September. An accord was reached tying future pay increases to inflation. The carrier said that first-half fuel costs fell 15 percent to 680 million. Cargo traffic rose 11 percent in the second quarter, while passenger traffic rose 1.1 percent. The airline’ s shares gained 87 cents, or 7.7 percent, to close at 12.11. Separately, Air France and Alitalia SpA agreed to buy 2 percent stakes in each other as Europe’s second-and sixth-largest airlines deepen their partnership. |