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What are the necessary and sufficient conditions for judging mathematical problems in comprehensive management?
(1) is neither a sufficient condition nor a necessary condition.

For example, a= 1, b=2 and c=3 satisfy AB 2.

A=2, b= 1, c=-3 satisfies a+b+c=0, but does not satisfy ab 2.

(2) It is neither a sufficient condition nor a necessary condition.

For example, a=-3, b=2, c= 1 satisfies AB 2.

A=-3, b=0, c= 1 satisfies a.