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问题 填空题

若a，b∈R，则a2+b2＜1是|a|+|b|＜1成立的______条件．

答案

∵a2+b2＜1时，（a，b）在以原点为圆心以1的半径的圆内，

此时|a|+|b|＜1不一定成立，

故a2+b2＜1是|a|+|b|＜1的不充分条件；

但当|a|+|b|＜1时，a2+b2＜1一定成立

故a2+b2＜1是|a|+|b|＜1的必要条件；

故a2+b2＜1是|a|+|b|＜1成立的必要而不充分条件

故答案为：必要而不充分

单项选择题

Heidi Krueger, CFA, has discretionary authority over the accounts of Johnson, for whom she manages a portfolio of energy stocks, and Osaki, for whom she manages a diversified portfolio of domestic and international stocks. Krueger always seeks the best price and execution and has disclosed to all of her clients the process she follows to make use of soft dollars and apply them for the benefit of her clients. In the year 2004, Krueger applied soft dollars generated from the Johnson and Osaki accounts to purchase a report on the economic impact of world events, to purchase an analysis of the domestic steel industry, and to purchase a new conference table for her office. Krueger was in compliance with the Code and Standards in the year 2004:（）

A. only if she had not used soft dollars to pay for the conference table.

B. only if she had not used soft dollars to pay for the conference table and had not used soft dollars from the trading of Johnson’s account to pay for the report on the domestic steel industry.

C. because she disclosed her use of soft dollars and applied them for the direct and indirect benefit of her clients.
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