A-A+
For any numbers a and b ab=ab(3-b). If a and
问题详情
For any numbers a and b, ab=ab(3-b). If a and ab both represent positive numbers, which of the following could be a value of b？
A．-5
B．-2
C．2
D．4
E．7
参考答案
正确答案：C
解析：The most direct approach to this sort of problem is to plug in the answers and see which one works. Choices A and B are out because any negative value for b would result in a negative value for ab if a is positive. C works because it gives the result ab=2a, which has to be positive. D and E do not work because they result in negative values for ab. Therefore, C is the only answer that provides a possible value for b.
