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标题: 问一道数学题 [打印本页]

作者: huangsiyan 时间: 2011-3-25 07:09 标题: 问一道数学题

If b, c, and d are constants and x2 + bx + c = (x + d)2 for all values of x, what is the value of c?
(1)d = 3
(2)b = 6

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.

我想请问，当把 x2 + bx + c = (x + d)2 化简后，得到bx+c=2dx+d^2,这个时候可以直接说bx=2dx, c=d^2吗？如果可以，为什么？

如果不可以，那就问答案为什么是D?

作者: michael_wind 时间: 2011-3-25 20:47

完全平方嘛，知道b，d当中任意一个就知道c啦~
你问为啥，因为一一对应，x的一次项和一次项对应，常数项和常数项对应

作者: danni423 时间: 2011-3-27 19:51

1) If d = 3, then c=9
2) if b= 6, then d=3, c=9

DD

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