ç±å·²ç¥å¾ |a|=4 ï¼|b|=3 ï¼
å 为 (2a-3b)*(2a+b)=4a^2-4a*b-3b^2=64-4a*b-27=61 ï¼å æ¤è§£å¾ a*b= -6 ï¼
æ以ï¼ç± |2a-3b|^2=4a^2-12a*b+9b^2=64+72+81=217 ï¼|2a+b|^2=4a^2+4a*b+b^2=64-24+9=49 å¾
|2a-3b|= â217 ï¼|2a+b|=7 ã
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