题目

已知a=(2,-3,5),b=(-3,1,-4),求a+b，a-b，|a|，8a，ab. 答案：解析：a+b=(2,-3,5)+(-3,1,-4)=(-1,-2,1), a-b=(2,-3,5)-(-3,1,-4)=(5,-4,9),,8a=8(2,-3,5)=(16,-24,40),ab=(2,-3,5)?(-3,1,-4)=-29.

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