【单选题】【消耗次数：1】
设 R={0,10,20,31,21,32,3}，则关系R的二次合成R○R等于：
①
{0,20,31,3
②
{1,02,03,02,13,13,2
③
{0,10,20,31,21,3
④
{2,3}.
参考答案：
复制
纠错
相关题目
【单选题】
设 R={0,10,20,31,21,32,3}，则{1,2}在关系R下的像R[{1,2}]等于：
①
{0,20,31,3
②
{1,02,03,02,13,13,2
③
{0,10,20,31,21,3
④
{2,3}.
【单选题】
设 R={0,10,20,31,21,32,3}，则关系R在{0,1}上的限制R?{0,1}等于：
①
{0,20,31,3
②
{1,02,03,02,13,13,2
③
{0,10,20,31,21,3
④
{2,3}.
【简答题】
设 R={0,10,20,31,21,32,3}，求关系R的二次合成R○R。
【简答题】
设 R={0,10,20,31,21,32,3}，求关系R的逆关系R-1。
【简答题】
设 R={0,10,20,31,21,32,3}，则关系R在{0,1}上的限制R?{0,1}等于：[填空1]
【简答题】
设 R={0,10,20,31,21,32,3}，求{1,2}在关系R下的像R[{1,2}]。
【简答题】
设 R={0,10,20,31,21,32,3}，求关系R在{0,1}上的限制R?{0,1}。
【单选题】
设 R={0,10,20,31,21,32,3}，则关系R的逆关系<img class=jc-formula style=vertical-align: middle; src=https://huaweicloudobs.ahjxjy.cn/C60082AF1C54FFA5A63D2879E701543A.png data-tex={ R }^{ -1 }/>等于：
①
{0,20,31,3
②
{1,02,03,02,13,13,2
③
{0,10,20,31,21,3
④
{2,3}.
【单选题】
设一个关系模式为R(A,B,C),对应的关系内容为R={{1,10,50},{2,10,60},{3,20,72}{4,30,60}},则δB>15(R)的运算结果中具有的元组个数为（ ）。
①
1
②
2
③
3
④
4
随机题目
【简答题】
<img src="https://huaweicloudobs.ahjxjy.cn/138789FD6E66C1069A825C3BB7988C61.png" title="9.png" alt="9.png"/>
【简答题】
用消元法解线性方程组<img src="https://huaweicloudobs.ahjxjy.cn/6905AFAB250E737807C46925B1AAAAA7.png" title="3.png" alt="3.png"/><img src="https://huaweicloudobs.ahjxjy.cn/7431B7E8919E06BBA67328C631475CE4.png" title="x1.png" alt="x1.png"/>[填空1]，<img src="https://huaweicloudobs.ahjxjy.cn/9EC7EF50C7C734EA70834C00143C7E66.png" title="x2.png" alt="x2.png"/>[填空2]，<img src="https://huaweicloudobs.ahjxjy.cn/8FEE7AAB6ED3CB1B2BAC443126B1F165.png" title="x3.png" alt="x3.png"/>[填空3]。
【简答题】
<img src="https://huaweicloudobs.ahjxjy.cn/F2519D3A617E8FA6E03BA9AB35D6002E.png" title="5.png" alt="5.png"/>=[填空1]
【简答题】
Translate the following sentence into English.在会上，他们讨论了如何保持师生间的沟通渠道畅通。
【简答题】
Direction: Fill in the blanks with the words given below. Change the form if necessary.[privilege; component; stagnant; entangle; superficial; arresting; expound; penetrating; indulge; click]5.None of them contain the[填空1]that you need.
【简答题】
Direction: Fill in the blanks with the words given below. Change the form if necessary.[assumption; contact; cliff; equivalent; emergency; outweigh; height; rummage; vibration; bugbear]6. The most maddening problem, however, was[填空1].
【简答题】
Direction: Fill in the blanks with the words given below. Change the form if necessary.[expand; abuse; knowledge; narrative; plantation; property; oppressive; extremely; rebel; abolitionist]2. The British had regarded jury trials as a potential bulwark against[填空1]actions by the king.
【简答题】
Direction: Fill in the blanks with the words given below. Change the form if necessary.[privilege; component; stagnant; entangle; superficial; arresting; expound; penetrating; indulge; click]9. The policy would[填空1]the nation in conflicts that could easily lead to war.
【简答题】
Direction: Fill in the blanks with the wordsor phrasesgiven below. Change the form if necessary.[toddler; lottery; claim; retract; turn down; somehow; in reality; gamble; publicity; inculcate]1. I had a[填空1]at home and two other children at school.
【简答题】
为什么说中国共产党成立是“开天辟地的大事变”？