2. 职称英语
  3. [img]2014m9x/ct_egreqm_egreqbj_0083_20148[/img] [br] DIn this question, you are

[img]2014m9x/ct_egreqm_egreqbj_0083_20148[/img] [br] DIn this question, you are

游客2024-01-12  14
问题 [br]
选项
答案 D
解析 In this question, you are given that(x + 3)(y - 4)= 0, and you are asked to compare the product xy with -12. Since(x + 3)(y — 4)= 0 and the product of two numbers can equal 0 only if at least one of the numbers in the product equals 0, you can conclude that x = -3 or y = 4, or both.
    Consider the case x = — 3. When x = -3, you can choose any number as the value of y and the equation(x + 3)(y - 4)= 0 will be satisfied. Depending on the particular value of y you choose, the product xy may be greater than, less than, or equal to -12. For example, if y = 1, then xy = -3 is greater than -12; and if y = 10, then xy = -30 is less than -12.
    Since different examples for the value of y yield different relationships between Quantities A and B, the relationship cannot be determined from the information given. The correct answer is Choice D.
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