题目: 若向量a=(1,1),b=(-1,1),c=(4,2),则c可用a,b表示为______. 答案: 设c=xa+yb则(4,2)=x(1,1)+y(-1,1)∴4=x-y2=x+y解得x=3,y=-1∴c=3a-b故答案为3a-b
题型:选择题 —Have a nice day to you.—_________.[ ]A. Well done. B. Thank you.C. My pleasure. D. Me, too. 查看答案