齐次线性方程组Am×nXn×1=0有非零解的充要条件是( ).A.r(A)<n B

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问题:

齐次线性方程组Am×nXn×1=0有非零解的充要条件是( ).

A.r(A)<n

B.r(A)≤n

C.r(A)<m

D.r(A)≤m

考点:在职联考GCT(数学)工程硕士(GCT)数学
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由方程3x+4y=5变形,用含y的代数式表示,则x=______.

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Malls are popular for Americans to go to. Some people spend       much time at malls that they are called “mall rats”. Mall rats shop until they visit hundreds of stores.
People like malls for many       . They feel safe because malls have police stations. Parking is usually       , and the temperature inside is always fine. The newest malls have beautiful rest areas with waterfalls and large green trees.
The       mall in the United States is the mall of America in Minnesota. It covers 4.2 million square feet. It has 350 stores, eight night clubs, and a large park! There are parking spaces for 12,750     . About 750,000 people shop there every week.
The first mall in the United States was built in 1965 in Edina, Minnesota. People love doing all their shopping in        place(s). More malls are built around the country. Now malls are like town centers where people come to       many things, they shop, of course, they also eat in food courts that have food from all over the world. They see movies at theaters. Some people even get their daily        by doing the new sport of “ mall walking.”         go to malls to meet friends.
In some malls, people can see a doctor or a dentist and even go to the church. In other words, people can do just about         in malls. Now people can actually live in their favorite shopping center.
小题1:
A.tooB.veryC.quiteD.so
小题2:
A.reasonsB.placesC.productsD.kinds
小题3:
A.expensiveB.difficultC.freeD.quick
小题4:
A.newestB.largestC.tallestD.biggest
小题5:
A.bikesB.carsC.shipsD.buses
小题6:
A.oneB.twoC.threeD.four
小题7:
A.seeB.watchC.doD.buy
小题8:
A.activityB.studyC.projectD.exercise
小题9:
A.The otherB.The othersC.OthersD.nothing
小题10:
A.somethingB.everythingC.anythingD.nothing
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B.将危险工序一端布置在人多地城市

C.靠近道路建立工厂

D.危险品生产区应与重要设施保持一定的安全距离

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