日用燃油柜应设自闭式液位计,液位计不得用塑料管制作
正确
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若向量α=(1,-2,1)与β=(2,3,t)正交,则t=()
求向量组α1=(1,2,-1,4),α2=(9,100,10,4),α3=(-2,-4,2,-8)的秩和一个极大无关组.
We_________thelessons_________oflastmonth.
__________ofthelandinthatdistrict__________coveredwithtreesandgrass.
ThisisthefirsttimethatI_________atthemeeting.