Question

设a,b,c都是正数,则必有（a+b+c)(1/a+1/b+1/c)为?

Answer 1

（a+b+c)(1/a+1/b+1/c)

=1+a/b+a/c+b/a+1+b/c+c/a+c/b+1

=3+(a/b+b/a)+(a/c+c/a)+(b/c+c/b)

≥3+2√(a/b×b/a)+2√(a/c×c/a)+2√(b/c×c/b)

=3+2+2+2

=9

选：C,大于等于9

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