题目内容
设A，B分别为m×n及n×s阶矩阵，且AB=O．证明：r(A)+r(B)≤n．
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设α1，α2，α3，β1，β2都是四维列向量，且｜A｜=｜α1，α2，α3，β1｜=m，｜B｜=｜α1，α2，β2，α3｜=n，则｜α3，α2，α1，β1+β2｜为( )．
党章对党的建设提出的四项基本要求是坚持______。
Learn about Noble Gases① Have you ever ridden on a balloon Many tourist spots offer balloon rides in order for people to see the beauty of a place from above. A balloon contains a noble gas called helium. Formerly, balloons contained hydrogen but hydrogen is very flammable and dangerous when uncontrolled. Therefore, people shifted to helium, which is safer. Helium is safe because it has the properties of the noble gases.② People once believed that noble gases couldn"t chemically react at all. For this reason, they were called inert gases. They were also listed under Group 0 in the old periodic table because scientists believed that the gases have zero valence electrons in their outer shell. This was later proven to be untrue when some noble gas compounds were discovered.③ The gases are elements, which share similar properties. These properties include being monatomic, colorless, odorless, being able to conduct electricity, and having low chemical reactivity. Noble gases include Helium, Neon, Argon, Krypton, Xenon and Radon. These are all found in Group 18, in the rightmost column of the periodic table. If you look at the periodic table, you will notice that these elements are the only ones, which do not have a charge. Helium has the lowest molecular weight while Radon is the heaviest.④ Remember that chemical reactions occur because atoms have valence electrons, which are electrons in their outer shell. When the outer shell is "unfilled" or the required number of electrons is not yet complete, the atom is more reactive. Noble gases have a full outer shell, meaning that they have complete electrons in their outer shell. This complete number varies. For instance, the outer shell of Helium has 2 valence electrons while the outer shell of Xenon has 8 electrons. Nowadays, there remains to be a few noble gases because of the low chemical reactivity of these said gases.⑤ Because of their properties, noble gases have many important applications. They are widely used in medicine and industries. For instance, liquid Helium is used for superconducting magnets. These magnets are very important in physics and medicine. When a doctor suspects that a person"s brain has been damaged, he might request for Magnetic Resonance Imaging(MRI). MRI allows the doctor to "see" the brain, without operating on the patient. Paragraph②______
编写函数fun，它的功能是：利用以下所示的简单迭代方法求方程：cos(x)-x=0 的一个实根。迭代步骤如下：（1）取 x1 初值为0.0；（2）x0 = x1，把x1的值赋给 x0；（3）x1 = cos(x0)，求出一个新的x1；（4）若x0 - x1的绝对值小于 0.000001，执行步骤（5），否则执行步骤（2）；（5）所求x1就是方程 cos(x)-x=0 的一个实根，作为函数值返回。程序将输出结果Root=0.739085。注意: 部分源程序在文件PROG1.C中。请勿改动主函数main和其它函数中的任何内容，仅在函数fun的花括号中填入你编写的若干语句。给定源程序：#include#includefloat fun(){}main(){printf("Root =%f\n", fun());NONO();}
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