2. 职称英语
  3. It x and y are integers and x =[img]2015m7x/ct_egreqm_egreqjs_0043_20153[/img],

It x and y are integers and x =[img]2015m7x/ct_egreqm_egreqjs_0043_20153[/img],

游客2025-02-24  28
问题 It x and y are integers and x =, which or the following could be the value of y ?
选项 A、15
B、28
C、38
D、64
E、143
答案 B
解析 To simplify the equation x =, divide the numerator and denominator of the fraction by 39 to get x =. From the simplified equation, you can see that x is an integer if and only if y is a factor of(2)(4)(5)(7)(11). To answer the question, you need to check each of the answer choices until you find the one that is a factor of(2)(4)(5)(7)(11).
Choice A: 15. Since 15 =(3)(5)and 3 is not a factor of(2)(4)(5)(7)(11), neither is 15.
Choice B: 28. Since 28 =(4)(7)and both 4 and 7 are factors of(2)(4)(5)(7)(11), so is 28.
You can check the other choices to confirm that none of them is a factor of(2)(4)(5)(7)(11). The correct answer is Choice B.
This explanation uses the following strategies.
Strategy 5: Simplify an Arithmetic or Algebraic Representation
Strategy 8: Search for a Mathematical Relationship
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