因为ab=|a||b|cos120=2*5*(-1/2)=-5
（2a-b)*a=2a^2-ab
=2*2²+5
=13
已知向量a和b的夹角为120度,且|a|=2,|b|=5,则(2a-b)*a=?
已知向量a和b的夹角为120度,且|a|=2,|b|=5,则(2a-b)*a=?
数学人气：415 ℃时间：2020-03-15 03:27:35
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