若平面向量a,b,满足|a+b|=1,a+b平行于x轴,向量b=(2,-1),则向量a=
人气:476 ℃ 时间:2020-02-15 23:26:36
解答
设向量a=(x,y)|a+b|=1(a+b)²=1a²+2a·b+b²=1a²+2a·b+5=1a²+2a·b=-4a+b=(2+x,y-1)‖x轴则a+b斜率为0y-1/2+x=0,y=1,且x≠-2a²=x²+12a·b=2(2x-1)=4x-2x²+1+4x-2=-4...
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