|3a-2b|^2=9a^2-12a·b+4b^2=9,其扒磨中a^2=b^1=1所晌搜以春谨斗a·b=1/3|3a+b|^2=9a^2+6a·b+b^2=12所以|3a+b|=2√3
|3a-2b|^2=9a^2-12a·b+4b^2=9,a^2=b^1=1,所以灶或族隐弊12a·b=4。|3a+2b|^2=9a^2+12a·b+4b^2=17,团搏|3a+2b|=√17